Relationship issue..

I think my boyfriend is lying to me about where he was this weekend. He told me he would be at this little like idk festival thingy w that goes on near our town with his grandpa and his bestfriend. He is supposed to come to my house tomorrow so today I was getting him his favorite drink at a gas station. And I seen one of his friends (were gonna call him ben and we are gonna call my boyfriend Tim) there and our conversation went like this:

Me: hi

Ben: hey have you talked to Tim today

M: yeah earlier but he is probably at that festival thing now because that's where he was gonna be this whole weekend

B: oh

M: why?

B: i was just wondering where he was, I was with him last night and Friday night though

M: at the featival thingy?

B: no

M: what? (When i said "what" i definitely sounded confused and mad)

B : oh no its was at the festival

and then he left.

It seemed like his friend was like covering for him so I wouldn't be upset with Tim. And now idk if I'm being paranoid or if he is being shady. I want to ask Tim about it but what if he just lies to me.