Locked To Owner

Last Year I try help my father he wanna install app in appstore but he forgot the password and also his password yahoo email so i try and i think reset to factory will be solve the problem i watched youtube how to reset it (as a Android User Never use any apple device)it come out locked to owner , so i feel guilty and responsibility i try to fix it i go to apple center in my region 3 times different store but they cant help me,

proof of puchase already gone since my father buy ipad mini 4 in 2017 and i asked same question in apple community in reddit they all too rude thought my father ipad is stolen ipad they mocked me instead help me :(( , yesterday i still see my father still try to fix his ipad, so right know theres a solution to fix my father ipad??

i feel guilty and its my fault :(( i planing to buy him another ipad but right know i dont have enough money to buy it :(