Why would the oil light stay on if your 1996 Toyota Camry has enough oil?

I recently purchased a 96 Toyota Camry and while driving it home (approximately 100 miles) the oil light came on. My mechanic told me after fixing it that it was a plugged prefilter screen before the oil pump causing the oil pump to be starved (most likely due to sludge buildup from infrequent oil changes and being parked for long periods of time while it was in the process of being sold.) Not the only scenario, but that's what happened to me.