It's all about the tags. You have to work in the other direction. Find something well-tagged, then giphy the fully qualified tag that produces the same gif every time.
Granted, this is not a "search engine" type of use case, but the actual existence of some gifs, and the tags applied, force a degree of compromise.
I am not the one that got $50M in funding though, I just want to use their one line integration on slack. That's up to them to make it not work, not me.