I just rewatched this movie and happened to notice this..
Do they ever acknowledge how they get the remote car back out of the evidence room? Unless it all happens in the same day (and we know it doesn't), there's no way someone wouldn't have noticed the open box on the floor and the remote car somewhere in the room. Wouldn't that have been super suspicious?
They never did. And since they didn’t, well that means this mystery is unimportant. You simply have to let this small thing go and forget about it altogether — like so much of this franchise requires you to do.
But if I must throw in a theory, then there is the possibility Tej “drove around” the room and looked for a good enough cover for the remote car (a table or something). What else was he going to do? His options were pretty limited.
The opened box? Methinks the writers thought... “no one will care about this”. Then again, maybe the gang figured that, other than Reyes, no one else was going to be hanging around the evidence room long enough to notice anything unusual. I mean a lot more unbelievable things happen in the F&F movies. :)