Click on the links below for the identifications of the alarm and computer locations. There are 2 different systems that Toyota used. You should either have the control computer under the seat as in the diagram below or the security light in the dash as in the other diagram below. If you have neither of these the system is not a Toyota alarm. An after market alarm sometimes will have a hidden valet switch usually in the left kick panel or lower finish panel. You will just have to keep messing with the battery connections or the door locks to get the right combination to get it started. You could always take a jumper wire to the starter from the battery to over ride the starter kill circuit. Put the key in the on position and jump the small wire at the starter. If it is an after market this might let you get it started so you do not have to tow it.
It is visible the box is about 4 inches square 1.5 inches thick and sits on top of the carpet.