I too have a Masked Picnic Raider, his exploits are many and legend:
The time he scaled a 15 foot cliff to raid the beach picnic I had just hauled him off - yep, same one twice;
The time he worked his way down a whole line of picnics on the beach;
The time a woman fell flat on her face sprinting back to defend her picnic;
The time he stuck his head through the fence of a gundog scurry and raided the picnic of a spectator!
The only picnic that has been safe was a naturist picnic on Holkham Beach - very sensible dog, most unhygienic having sandwiches naked
You are SO not alone