I always have a few leaves in the filter. When leaves get to the air vents, they dry out, get smaller, then the A/C fan drags them in.
P.S. It is not a good idea to leave the A/C on recirculating, as you could get a build up of CO2 which is not good for you, plus mould, electrical stuff don't like moisture. Read below..
https://www.thecarexpert.co.uk/why-air-conditioning-recirculation-is-important/