YOU is in a straight line but VEE isn't. However - unbelievably - there's also TEETEE, which is. And so is UU (= W?), but they can't all be forced into one straight line.
I'm getting so crazed now that I seriously thought that BBTEETEE might signify 'four consecutive letters in a straight line', pointing to an echo of the puzzle's title as rendered by a stammerer: 'Let's d-dig for the b-buried t-treasure, you f-fellows!'