I'm looking for more info on this sticker, so far I've found it to be on 2 different TI-83 Plus that both have the Factory/Date/HW of I0299A and are somewhat close in serial.

I'm wondering if anyone else has a calc with this sticker and if they have any clue if it was added by TI or some school or something.

I have a TI-83 Plus with the same factory and it doesn't have any such sticker on the back of it. Personally, I HIGHLY doubt that TI has put this sticker on any 83+ because the warning seems overblown. Lot's of the information is true, though. If you see the warning you should probably replace the batteries or else you will pretty soon have a dead calculator. If your calculator batteries do die though, you will lose any unarchived programs and data. Any archived programs/data will not be lost. However, the reference to performing the garbage collection cycle indicates that this is most likely not from TI because all a garbage cycle does is rearrange programs and variables into consecutive blocks in memory so that some memory is freed up. I'm not sure why you would want to run garbage collect cycles after replacing batteries, as I've never had any issue with losing memory after replacing batteries. So I'm pretty sure that this is something that was probably added by a school or an individual.

Your TI-83 Plus is K-0611T, which is twelve years after what this sticker was found on. It is an official TI sticker, which you can tell from the sku in the bottom right "83PL/LB/1L1/A".

For entertainment I scanned mine with my phone

This sounds to me like someone got paranoid that the calculator wouldn't correctly write Flash memory with low batteries, and/or would end up with some sort of partially writes (hence the memory corruption warning and the garbage collection instruction). As Logical says, that's definitely an official sticker.