First you have to find out the snapshot# with RPC:
snapshotnum = chains/main/head/context/raw/json/cycle/CYCLE#>/roll_snapshot
Then you get the level that snapshot was. heres how its done in python, showing the constants that are used:
snapshotlevel = ((<CYCLE> - constants['preserved_cycles'] - 2) * constants['blocks_per_cycle']) + ((int(snapshotnum) + 1) * constants['blocks_per_roll_snapshot']))
Then from that level you just RPC to see what all accounts were delegated at the time of the snapshot:
chains/main/head/context/delegates/<YOUR DELEGATE PKHASH>
The list displayed will include your delegate pkhash (if it did make it into the snaphsot) along with anyone else delegated to your pkhash (if they also made it into the snapshot).