According to the patch notes:
“Cosmic Signature scanning progress will now be saved until the client is restarted. A session change should no longer clear scanned signatures of any percent. Combat targets like ships and citadels will not be persisted.”
I scanned down two different wormholes with over 13 signatures each. The first time I came back to one WH, the sigs were indeed saved. About an hour later, without restarting my client, I reentered that same WH, and none of the sigs were saved.
Same thing for the other wormhole, upon my first return visit, none of the signature scan results persisted in my probe overview.
Seems like CCP is on the right track, but still not totally working as intended.