OK, after a night to think about it, OP should be writing a SCATHING letter/email to Tumi management. Not just customer service, spend some time to find some real email addresses of real people at Tumi HQ.

Letter/email should discuss what exactly happened - short and sweet. How this premium priced messenger bag snapped after only owning for a short time, how your laptop was damaged as a result, and how you were sent out of a repair shop to your client meetings, with a paper bag.

Also, you need to express what you want them to do for you now. Just complaining is one thing, but what should Tumi do for you now? That needs to be clear in your letter/email as well. Maybe they should overnight you a loaner bag, and reimburse you for the laptop repair?