Imagine the following scenario: you’re walking back home at night and pass through a dark alley; suddenly you see, a few steps ahead, an obscure figure lurking in a corner; you startle and freeze; you get somewhat frightened; for a second or two you’re certain there is a threatening presence over there, you’ll get mugged or worse …; and then you realize, with considerable relief, that it’s just the shadow of a tree stub; you calm down and move on, but in your mind you keep an image of the “Dark Lurker”, as you’ve spontaneously dubbed the figure (the imaginary figure you saw, not the mere shadow of the tree stub), for quite a while longer. When you later think back to the episode, or talk about it to friends, you continue using that name, the “Dark Lurker”, which has become a useful shorthand (although it no longer comes with the emotional intensity it had at the time).
4. Now I’m not, of course, suggesting that the “Dark Lurker” is a momentary god: I made up the scenario merely in order to have a foil for comparison and some exploration. But note that it does have all the features Usener and Cassirer listed: it’s an everyday situation, a subject has a percept accompanied by a strong affect (fright, in this case), and then imagines and names an entity which is bound to that particular episode.

It also coincides with something else Cassirer points out about momentary gods:
The image of the momentary god, instead of merely preserving the memory of what he originally meant and was — a deliverance from fear, the fulfillment of a wish and a hope — persists and remains long after that memory has faded and finally disappeared altogether. (Language & Myth, 35-36)
Whatever it is that the name “Dark Lurker” refers to, it’s not primarily something connected with the memory of the episode. The name is not used to recall, and make vivid again, the emotions itself which the person had in the episode. True, these emotions did lead to the naming: without the intense fright, the whole episode might have gone by without the positing of an entity that is the “Dark Lurker”. But once they’ve played their part, the emotions themselves (along with the percept, i.e. the sense impressions and the seeing of the tree stub shadow as the figure of a person) are no longer required. The name has come to signify something quite apart from them, and one doesn’t need to feel them for its use. They’re not needed, that is to say: to revive the experience, to make it vivid again to the person; and obviously, they’re not required for the friends to understand the episode when they hear about it, either. None of the friends has to visualize the same percept or empathically feel the same fright — they might do that, but it’s not required for them to understand the scenario and the correct use of the name.
Strictly speaking, this does not exclude all forms of memory the subject may have of the situation. It excludes only the subjective phenomenology of the experience itself: the affective quality, but also the seeing-as (seeing the tree stub shadow as a figure). These are precisely what is restricted to the subject and the actual situation, the “here and now” and the “for me” in that particular episode. The same subject, at a later time, does have some memory of the episode (otherwise they wouldn’t be able to even narrate it to their friends); but for the name of the “Dark Lurker” to be used, it’s not necessary that their memory includes all the subjective phenomenology. And evidently, the friends do not need any of that either: they might empathize to some degree with the affect, but that goes only so far; and obviously, they won’t have the percept, either (of seeing the tree stub shadow as a figure).
I think that must be what Cassirer had in mind when he speaks of “objectification”, in the passage I’ve already quoted once:
it is something purely instantaneous, a fleeting emerging and vanishing mental content, whose objectification and outward discharge produces the image of a “momentary deity”. (Language & Myth, 18)
The idea seems to be that, although we’re talking about particular situations, an individual subject, and a transitory state of mind, somehow creating and naming an image (the “momentary god”) moves us out of the purely instantaneous and subjective state into something (comparatively) objective. The image of the god, Cassirer says, has a “tendency to permanent existence”, and he draws the parallel of this area (mythical images) with language:
The same function which the image of the god performs, the same tendency to permanent existence, may be ascribed to the uttered sounds of language. The word, like a god or demon, confronts man not as a creation of his own, but as something existent and significant in its own right, as an objective reality. As soon as the spark has jumped across, as soon as the tension and emotion of the moment has found its discharge in the word or the mythical image, a sort of turning point has occurred in human mentality: the inner excitement which was a mere subjective state has vanished, and has been resolved into the objective form of myth or of speech. (Language & Myth, 36)
This “tendency to permanent existence” and the “objective form” (attributed to myth and language; i.e. not the god is an objective form, but the symbols which refer to that god) in which it results (“is resolved”; the original has “ist aufgegangen”) are the most interesting ideas here. Without these, we would be merely talking about figments of the imagination — that’s what the “Dark Lurker” surely is, but “momentary gods”, in some interesting way, go beyond that.