Yeah, I have Premium, but I was busy with work last week, so I missed like 99% of the event.
Also playing a match for like 45 minutes only to have it crash at the ending screen and not save any XP/Unlocks whatever about had me at full rage capacity.
I've probably wasted about at least 5 hours of gameplay with no progress towards unlocks, and I'm already sick of unlock systems as it is.
If the client crashes, then your unlocks should be saved and sent to Battlelog via the server. Just wait for the round to end and they will pop up.
If the server crashes, you lose all of the data. I haven't experienced the latter in a long time though.
Note: If you crash do not rejoin the game or the server will overwrite your stats with the new ones. If you are having a bad game, by all means, rejoin and have another crack at it. If you want to keep those stats, just stay out until the round is over.