Delayed
I had a flight that was supposed to depart at ~6pm today. At 3:46, I received an email saying the flight was delayed 40 minutes.

Canceled.
About 40 minutes later, I overheard a co-worker mention that his flight was cancelled. We were on the same flight . No notice from Delta.

Reaction
I realize my flight is the last DL flight and I burst into action and called the diamond desk to try and get re-booked. Agent answers and I try to re-book from several airports within 100 miles, but I can't make any of the flights

I ask the cause of the cancellation. I'm told that it was due to air traffic. I challenged this and even the agent said he had never heard of a cancellation due to traffic, only delays. After 10 precious minutes on hold, the agent came back on and told me it was mx. So, I try to re-booking and all but the last flight to O'hare is Y0. The only connecting flight to ATL on AA is canceled.

Questions
Why didn't I get a notification or call? I'm 100% certain I could have made another flight at a close airport with another 15-20 minutes notice. I'm also pretty confident that those flights weren't oversold until my flight was canceled.

I'm mad I didn't get a call and that I was re-booked on the 3rd flight the next morning. Can't switch to anything earlier. I thought i had protection priority?

So, now that i'm not going anywhere, what should i complain about and what compensation should i ask for? Let me add, there were 7 remaining flights to DFW, CLT, ORD, EWR, and LGA. I should have had plenty of options.