Well, I piled the kids into my 2008 Prius, found it wouldn't start - showing the 'no key' symbol. Got out, locked the door. Piled the kids into spouse's car, ran errand, returned. Time to see what's going on with the Prius. Car won't unlock. Changed the battery, restoring the little red light in the corner of the fob, car still won't open. Only one fob, no metal key. I don't know if it is the fob, the transducer thingy in the car, the battery, anything. I'd really appreciate some help with next steps. Should I get my insurance to tow it to my local garage (hybrid specialists, non-dealer), call a locksmith. Any advice would be very welcome! Thanks!
You are aware that if this is the original FOB that came with the car, there is a metal key hidden inside it, correct?
Bummer. Two keys and two fobs are non-negotiable when I buy. If the dealer won't supply them, I don't need the car that bad. So, now that the inevitable has happened, I'd think @bisco has the most straightforward temporary solution with the mobile locksmith. But it will happen again, so once you get the car running, which might or might not need a jump, the first thing on the list is to get a second fob and both keys cut. Your non-dealer hybrid shop is likely to have the best price assuming the place where you bought the car can't make it right. Nice thing about the Gen 2 is that it's a regular metal key, so they are cheap, but I think you'll need to get a code for the cutting pattern and that might be dealer only. Not sure.
There's also a tool that can be used to get the code for cutting the key when opening the lock. So it might be useful to try to find someone to make a key while unlocking.
call the dealer. You can give them the Vin number and they can cut you a new key from their Database. I did this years ago with my Nissan truck.
Just a quick 'thank you' for everyone's help. I called the tow truck, who decided to try to jump the battery first. Solved the problem! Apparently batteries can go flat when you don't drive often - and I've been working from home lately. I will take the advice to get a spare set, and a metal key cut! Thanks again!