relearn key fob? (after battery replacement)

I assume that your car has the SKS system? ie it has the little button on the outside door handles, the toyota symbol on the fob is silver, and you normally walk up to the car, it unlocks, and you power up and drive while the fob stays in your pocket.

First thing I would do is to look under the driver's dash at the steering column. There should be 2 buttons. One is for TPMS (tire sensors) and the other turns the SKS system on or off (might say"key"?) click the one for SKS and see if that does it.

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That seems most likely. Either that or both fob batteries died at once. If the car forgot the fobs, which does not happen just from disconnecting the 12V, then you would not be able to start it using the fobs -- even by putting them in the slot.