Thank you for the help everyone! The problem was actually not a problem after all.
After arguing with Xoom a few times over the phone, I went into the More Casa Central and spoke to the first worker I saw and explained what had happened, showed them the emails saying Transaction Completed and said that I spoke with Xoom customer service and that they confirmed the money had "been picked up" on Saturday. The lady looked up the transaction number and said that actually the money had not been picked up, and it was listed as an uncompleted transaction in the More computer system, and that the transaction was there in full waiting to be picked up. She said it probably was a Xoom computer error, that sometimes the signals "get mixed up" and that in the future I should call the More customer service number instead of Xoom because they have a better sense of the pickups. So, in the end, I picked up the money in full and went home. Really strange, but luckily Xoom continues to have a near perfect record!
She also assured me that for foreigners they always request passports and would never accept a copy of a passport or anything similar.