if it is still stuck in gear with engine switched off? then fault is selector/gearbox problem. if its now out of gear and you can select all gears with engine off ,clutch fault, with engine running can you put it in gear or can you only find neutral, if so then clutch not clearing, [could be cable or hydraulic fault,withdrawal mechanism faulty] make/model of car would help to give more accurate diagnosis!
k
May 2013