So now we need a volunteer to get two similar yeast smack packs or whatever they get their yeast in. Refrigerate one and leave the second out for a week or two. Brew two identical batches using the same method i.e. starter pitch temp, volume... Then let's see if there is any noticeable difference.
My bet is unless the warm yeast is in horrible conditions, it will be fine. The strain may change things as some can handle warmer temps better.
My LHBS has given me yeast that has had an old date on it, not too old. I always made a starter and never had a problem. He also got a Wyeast smack pack once that started to blow up before smacking or selling it. He put it on a top shelf and left it for months. It never exploded.