I signed up for cash + miles upgrades for flights to LHR and returning through MAD early this month and cancelled the upgrades (long story but got put on an another flight due to cancelled flight outbound and a schedule/plane change on the returning flight). The cash portion was refunded to my American Express card and the reservation record and my boarding passes show that I flew economy. The miles, to date, have not been redeposited.

I have made 4 phone calls:

Call 1: 3 days after the last leg. 1k operator transferred me to Mileage Plus, 35 minute hold, result: "Oh, it takes a few days for the miles to go back to your account."

Call 2:, 4 days later. 1k operator transferred me to Mileage Plus, 30 minute hold, hung up

Call 3:, 6 days later. Mileage Plus, 38 minute hold, operator told me "I'm not sure why this has not happened yet." I asked for a supervisor, after 18 minute hold, hung up.

Call 4, 10 days later: Mileage Plus, 20 minute hold, hung up. Called 1k line, asked for supervisor, 10 minute hold, supervisor called Mileage Plus, 16 minute hold, was told that they couldn't get a hold of Mileage Plus.

Supervisor said she would contact Mileage Plus the next day. I asked for a confirmation of this. She said she could not email me or give me a direct phone number but she took my cell number and promised to call me. She never did.

14 days later: After 2 weeks, the miles have still not been redeposited and I need them to redeem for another big trip requiring lots of miles. Meanwhile, upgrade seats dry up for my dates.

Lesson: Be very wary of redeeming upgrades and not having them used for any reason. You may may never see them again.