So sorry to hear about this. One of my friends put her bag (Birkin or Kelly) inside a recyclable bag when she boards public transport. You canWhile it's not surprising, I'm really sad about the security/theft issues raised here. My home lifestyle is so boring so I look forward to saving "special" things for vacation.
However I've yet to travel with my B30 - not primarily because of security issues at my destination, but because I don't want to damage it during transit. I am notorious for rubbing/scuffing handbag handles on my carryon suitcase's vertical bars/handle when I put it on top of the suitcase, and Birkin handles are too expensive to replace
I've travelled a bit recently with my Della Cavalleria as it's smaller/easier to carry and store away. However, even with the best precautions, fluke events just happen; I was recently on the Paris metro and as the doors were about to close a teenage boy literally divebombed into the carriage, ricocheting everyone sideways, including someone's heavy rucksack straight into my DC hardware... when does that happen?! Unfortunately DC's new deep scratches will always be a memory of that trip!
consider that.