Roy is looking for a job. He interviews with UPS and the interview goes ok. He is very qualified but spills hot coffee on one of the interviewers.

2 weeks go by and he gets a package in the mail saying he is offered a job. He thinks about it and sends in his acceptance on September 15th via the US mail. The mailman picked up the letter but stopped at the local bar for a few cold ones. Some rowdy kids torched themail truck while the mailman was in the bar. The letter never got to UPS. On September 18th UPS calls and says "the offer was cancelled". Roy says, I already accepted by mail.

Who is right? Is there a valid acceptance? Discuss.