I always heard they did, perhaps there is mention in the Young Mosaic set. I certainly don't remember any specific dates but there are tools such as ripmjazz and newspapers.com that one can use.
In the Iron City discussion a couple of months ago, some clever sleuths were able to find lots of documentation of Grant Green gigs with either Young or Patton, but this was the post-Elvin era.
If a specific date is pinned down, the next question of course will be...