drop/dump something in somebody's lap
drop (something) in (someone's) lap
To give to or force upon someone suddenly and unexpectedly. When Steve won the lottery, we suddenly had the chance to travel the world dropped in our laps. Our son dropped his student debt in our laps when he lost his job last year.
dump (something) in (someone's) lap
To foist something onto someone else, usually some task or responsibility. Yep, management dumped that big project in my lap after Lydia resigned.