I'm not a native English speaker, so I'm sorry if this is obvious but I can't find an explanation.
Why are "like"s usually referred to as
like's on Facebook? (You can see many instances here.)
To use a "word as a word" I would put quotes (if convenient using the apostrophe character in electronic text) around the word and place the plural -s outside them, and it seems that is the norm except on Facebook, e.g. "like"s.
By the way it seems the same applies to the "Discours particle" use of like, as @simchona says in the comments.