It takes a good couple of minutes for the majority of the oil to come out anyway so you most likely stopped just in time plus what celica do you drive as 3 litres does not sound much at all most cars hold at least 4-5, looking at your profile pic I will guess that you drive a gen 7 which in fact holds 5 litres, as for the sump bung if the threads were not stripped then the only reason would be that it wasn't tight enough, plus rule of thumb is that if it has a copper washer then they are pretty much a one hit only as the copper washer compresses when you tighten the bung up so once compressed it can't be compressed again to form another seal so that's why you should always put a new one on, you sometimes get a new washer in the oil filter kit if you buy a decent oil filter.
Basically next time when you do an oil change next, replace the washer and do the bung up fairly tight, a little trick I have learned is that change the oil when still warm that way obvious oil comes out quicker and metal expands when hot do you can do the the nut up tighter as if you tighten the sump bung when sump is cold then it may feel tight but as soon the sump gets hot along with vibration can cause the sump bung to come loose, if you do just want piece of mind then re tighten the sump bung after a couple of days.