I just had this happen to me after a service for the Takata airbag recall, battery replacement, and scheduled maint. No XM available as an audio source, icon disappeared.
Solution: I read someone fixed it by removing the fuse for the radio and turning on the 4runner, then turning off and replacing fuse, that didn't work. What did work was i found what connector connects XM to the car, and then i wiggled it and pushed in to seat the connection. Turned on the car on in my garage and immediately the XM icon was back. I found a page about how to remove XM radio icon, and basically did the reverse of that LOL. I wouldn't be surprised if the cable runs behind the air or something like that. The dealer assured me the head unit is absolutely not removed when replacing the passenger airbag.
Complaining about the dealer you don't have to read:
Dealer told me to talk to XM support and that it was normal for the xm icon to disappear, i asked twice to confirm because that's obviously BS. Left a yesterday with dealer service person saying that i talked to XM and they can't do anything, and called 4 times today to try to get the vehicle back in. Maybe they have caller ID. Luckily I had not completed my review of my service with Toyota yet.
Credit for the image goes to this dude:
Is there a hack to REMOVE SiriusXM as a source? | Toyota RAV4 Forums