Hi @MatthewWalsh,
Ah snapshots arent they grand 
???
Slightly confused how the data would be erased? If you were using the snapshot options within Sync you should have everything still?
Worst case give Phocas support a call, they may have backups of your system so you can get the sync feed, the problem here is that time may have elapsed and they are now lost due to thier backup rota.
What I do (extra Paranoid!):
- Get the query that you use to push the data to Phocas and insert it firstly into a local table on your business SQL server or Excel (if no DB option is available) and add a timestamp of when it was executed. You then have a local backup which will build over time, the challenge is how often are these snapshots? Monthly (managable), daily (awkward), hourly(not going to even think about).
- On this local “copy” you should have this new timestamp and then query this data using the timestamp to push though to Phocas via sync (without the timestamp).
- The sync snapshot should take it from there with the extra column that has been added as part of the sync.
Another advantage of having it local is what if there is an internet glitch when send the sync to Phocas? If its once a month you could loose your window of opportunity, its mainly for this reason I set up a local copy, so I have some peace of mind that the data is there and can force it though later.
I mentioned something similar when I made a huge mistake and needed to get the data out of Phocas here: Retain Snapshots - Inventory
Good Luck!
Jon