I just got the email you were talking about. Hm. It kinda sucks, but Ticketmaster MX has (in the past) been cool about it. They are strict about this rule, but willing to overpass it if you have a valid reason.
I went to Mexico to see 30STM a couple years ago and had this exact situation, and what I did was the following:
- I emailed them (in spanish), explaining that I had bought the tickets and understood will call was up to 48hrs previous to the show, and mentioned that I had a problem with that, since I was not arriving until the day of the show. (If you need help with the writing, I still have a copy of the email I sent them)
They answered and told me that, due to my specific situation, they had made an exception to my tickets and they were not going to be cancelled if not picked up 48hrs before. I was allowed to pick them up at the venue (which I did, on the day of the show).
(Their exact answer was: There is no problem, we have modified your order to ensure your tickets do not get cancelled. You will be able to pick them up the day before the show as you requested, or up to 2 hours before the show at the Venue Ticketing Office.
"No hay ningun problema, hemos modificado su cuenta para que sus boletos no sean cancelados y los pueda recoger en un centro Ticketmaster el dia 7 como me comenta o bien en la taquilla del evento 2 hrs antes.")
I hope this helps some! I have been told that they are otherwise rather strict with this rule. If you don't contact them chances are they will cancel the tickets! :S Let me know if you need a bit more assistance