Thanks for contacting Sophos Support.
In regards to this infection in particular.
I have discussed this with a colleague who can remember more details about this threat. Our thoughts are that it would be odd to suddenly get a false positive on Parite-B. It is pretty persistent nowdays, so may well reappear - perhaps via email, or even associated with another infection.
Since any of the newly infected files become a valid sample, it would be best if you submitted a copy of one of the files to SophosLabs - that way we can confirm the infection.
This threat is a file infector, which spreads by shares - so there must be one or more unprotected machines on the network. That is something you will have to verify.
Lastly, as to the deletion of your files - it is unfortunate. Sophos is set by default to do nothing when disinfection fails - for this very reason. You may wish to examine this listing of the remainder of defaults for AV and HIPS settings, in comparison with the remainder of your network settings.
Meanwhile, to submit a sample of the file, you can reply to this email, provided you zip and protect the file first. Here is a link for doing that online, if you prefer: Submitting samples of suspicious files to Sophos
If you do choose to submit the sample, please use the case reference from this email in the submission: [#902153]. That way, I will be able to track your submission of the file.
If you have any further questions, please reply to this email.