They could easily try that. But it seems better to possibly try a bit more digging first. Or, in Marty and Doc's minds anyway, regardless of whether they should be somewhere or not.

Which, well. What they do find when they check the cinema only raises more questions as a result of said curiosity, as Marty follows, about to respond when he also notices the owner.

"W-wait, what? Is this....me 'McFly' Or.....?"

To be fair, given the time of their destination, and previous encounters with his parents and kid with their adventures. It's not a bad question.