He moves quickly. He's used to situations like this, where a sudden duck and/or attempt at cover is sometimes the difference between escape or getting eaten. When someone signals you to do something, in a situation like this, you listen.

So he ducks under a table with a low-hanging tablecloth, pressing back against the wall, as the thing comes back, snuffling by again.

This time it passes and seems to leave. Maybe. In any case, they probably can't avoid its attention if it comes by for another pass. Dipper peeks his head out, edging out slowly and carefully, checking both ways to see if the coast is clear.

When it seems like they're clear, he silently signals for her to follow him in the opposite direction than the one the creature went down.

He doesn't even whisper a word. It's too risky to talk when that thing could come running back at the slightest sound.