Painless, white rough patch inside of cheek. had it last week then it went away and now it's back in the same place. can't be wiped off. what is it?

Two possibilities : First of all when you get dehydrated and and I dry mouth you can get white patches that can come and go. Secondly thrush type of candidal used infection can cause a white patch that when you scrape it off is right underneath. This usually requires topical oral antifungal rinse. If this persists see your doctor for further recommendations.