If it’s anything like the Fit... there should be a large opening above, where the flap that move to switch between fresh air and recirculation. And that opening is completely exposed for recirculating mode, in the Fit. I took a look at Hondapartsnow for their diagram of the blower.
HondaPartsNow.com offers the best deal for genuine Honda parts, 79305T7WA01. Blower Sub-Assy for $79.48. All parts are backed by the Honda's warranty.
www.hondapartsnow.com
The image that shows just the blower, shows the large opening I mentioned. The image that shows the blower and various other parts, shows smaller slats instead.
If it did fall in there, it won’t do anything for now. But it will fall further into the blower when it comes time to change the filter. And if you don’t retrieve it at that point, then it could potentially get chunked by the blower fins... if not breaking the blower fins themselves. Either case will most likely result in replacing the blower... automatically not covered by warranty, if you still have.
So yeah, get it out of where ever it might be to be sure.