Too bad he wasn't more specific. The "something" could have meant a piece of jewelry or some other item of sentimental value.
If you know the city where your grandmother died and her approximate date of death, figure out what the name of the county is for that city and then look at that county's online court records to see if she has a probate file.
If so, you can look at the probate file at the courthouse to get a copy of the will or see if you are mentioned in it.
In the meantime, you can look at online telephone directories (or hire a private investigator if you choose to do so) to search for uncle.