Car Alarms: anti theft device on car, gold lettering, rectangular piece

Question
I have a 2002 toyota sienna that I bought used and it had a small lucite rectangular piece that had to be near the key in order to start the car. The piece had black inside with gold lettering.  Today, it fell off of my keychain and I cannot find it anywhere. My car will not start without it * it's in a mall parking lot_) and I don't even know the name of the company that made the device.
A red light on a little black attachment is attached under the dash and it beeps a few times if you try to start the car.  The car just seems like a dead battery.  Is there any way to disable this thing?  Who do I call?  The car dealer that I bought the car from said they couldn't do anything as it was an after dealer install and they didn't have any information. HELP PlEASE.

Answer
Wish I had some good news, but without the coded
pass key, you will need to tow it to a circuit city,
best buys or any other can alarm installation shop.
(NOT TOYOTA!) and have that removed and then
return the car to pre installed condition.

Not what you wanted or needed to hear I know, but
that device is doing what it's designed to do.
Only thing left now is to remove it from
the mix.

Sorry about that.
Good luck.

ALARMTEK
CARALARMSTORE.COM