There are some cases already studied that the SSD when unpowered could suffer from data retention problems.
Crucial explains it here:
https://www.crucial.com/support/article ... smart-data"The Joint Electron Device Engineering Council (JEDEC) is the industry group which creates standards and specifications for semiconductor-based devices and assemblies. Micron is a leading member of JEDEC, which defines data retention in a specific way: For SSDs in client applications (like business or personal computers), data retention for an SSD shall be one year, in an unpowered state, stored at 30 °C (86 °F). This should give most computer users plenty of time to retrieve any data from an unused drive after some time on the shelf, if needed."
So, it could be that or it could be that the SSD was not very well stored (magnetic fields for instance...)