It actually happens, similarly to bird strikes or collisions with essentially any object that can float or fly into the path of a plane.

https://simpleflying.com/avianca-airbus-a319-balloon-strike/

https://www.latimes.com/archives/la-xpm-1994-09-22-me-41720-...

https://dronedj.com/2021/08/31/update-faa-says-envoy-air-pas...