I've had a number of SSDs in client systems fail, and I've had a couple of my own fail, and in nearly every case the drive has soft failed. The controller puts the drive into read-only mode, and you can still copy data back from the drive.
This can be quite strange to diagnose at first, some controllers tell the OS that they are read-only, but others pretend it's business as usual, and let you write data. They don't actually commit the data to flash, but tell the OS that they have. It can be difficult to work out what's going on the first time you see this - when you save a file it looks like the save operation has completed, but then when you open it again, it's magically gone back to how it was before.