If you bought the flight out on the Saturday, then you were not stranded in Mexico, and they are properly offering to refund your costs. I'd expect some miles for the stupidity of what they did. I've had a good will payment of a enough miles for a one way on the route and class for the route I was flying when there was a big snafu, and I'd be looking for something similar here.

You may also be entitled to EU compensation for being IDB'd which would be several hundred euros - it would depend if you were a volunteer or if you were refused check-in. Did the VS staff explain your rights under the EU, or give you a copy of your rights? They were required to do so under the EU law.