Y axis no home done message that damaged my print sheet and bed

I want to move the extruded and hotend out a bit to do maintenance but a message come up “axis y no home done! press ok to home”. I pressed ok button then the bed raised and crashed into the hotend leaving a big dent on the high temp sheet and heated bed. why did it do this? How do you home y axis without damaging the printer. not happy that it damaged the print sheet and bed and it seemed to put a lot of stress on the hotend and carbon rods during the crash.