Panasonic KX-TG2583B - undelete messages

The data stored in the flash memory is most likely compressed using some proprietary technique in the ASIC that runs the answering machine, so unless you have access to that just dumping the contents of the flash memory will probably be useless.

Unless there is some kind of undocumented feature that allows you to undelete messages, the only way I can think to get them back is to trick the microprocessor in the controller IC into reading from a different portion of the address space than is intended, i.e. the portion that contains your message. If the controller IC is something like this:

then it supports both parallel and I2C memory - the task will be easier if a parallel interface flash memory is used as you might be able to just disconnect some of the MSB address lines from the processor and manipulate them manually until it's reading back from the correct area. If it's an I2C interface then it will be more difficult, the only thing I can think of is putting a microcontroller between the answering machine chip and the memory that has I2C input/output capability and doing an "on the fly" translation of the address data.

Sorry to hear about your mother in law. I don't know which encoding they use or where the address pointer table would be stored in the NVRAM. I remember that you could delete messages via handset on some phones by pressing "7" from the menu. Can't remember the brand but there was an undocumented trick to press "77" to undelete.

Jim, just came to mind: If all else fails you could get a quote from a forensic data recovery place. Given the reason for your request, maybe they'll offer a discount, as they are usually expensive.