SSH Authorized Keys file deleted when upgrading fabric OS

I recently upgraded Brocade fabric OS (on a 6510) from the 7.2 family to the 7.3 family.
The upgrade itself went pretty flawlessly, however I noticed the authorized_keys file had been removed from /fabos/users/admin/.ssh/authorized_keys.admin

It was fairly simple to re-create it in there, but as a caveat, please back up this file or ensure you can re-generate it after upgrading Fabric OS.
SSH Key exchange doesn't seem to be a widely enough supported feature of Fabric OS for the vendor to have been a lot of help with the issue.