In general, resumes often have things on them that are difficult to verify. Unless they are so suspicious or odd that they will draw negative attention, or tend to make someone want to challenge it and ask for proof, it's perfectly fine to put it on the resume if it is relevant for the job you are applying for. I've done this myself, so it's not idle speculation.
As an example, I once finished top 10 in a competitive speaking competition at my college. I figured it shows that I would tend to give good presentations, so I listed it (and it remains on my academic CV, as there is no length restrictions on those). I never even got a certificate, though, and was only told the results in person - only the top 3 got any kind of prizes or certifications, and it never occurred to me to care. It would be even stranger to ask for proof of that though - it doesn't seem like a particularly grand claim.
As you get older and gain experience, especially when dealing with length restrictions like on resumes (where 1-2 pages is a pretty hard limit for most positions), they will tend to "age off" and it no longer is worth the space to mention it.