I think it would be very useful to be able to search and navigate in snapshots. Maybe it is not what snapshots are made for, but many people use it as a way to have two copies of the same pdf file (for instance, one for reading the text and the other for consulting references or solutions to exercises). In any case, I think that being able to find a keyword in a snapshot or going to an specific page ("Go to page..." feature) would be very useful.
Snapshots are images. Not text. Even if they may contain images of text. So there is nothing to search.