How much difference will it make?
I don't mean that snarkily, I am wondering if you can't just placeholder that section, keep going then come back when you decide. Or write it both ways and see which you like (a good writer's exercise, regardless).
Another plot movement trick I find works: deprive a character of something. Even something small like the last danish to go with their coffee. Or just spill their coffee. Amazing how well a small thing like that can spur action without jumping out like Deus ex machina.