I've had it happen on my trips .. but only really noticed because I had a fast pass for that time:
Once was for Winnie the Pooh
Second time was due to lightning storm (for 7DMT).
Both times . it was actually to my BENEFIT the rides were down because I was rewarded with a "use anytime later in the day" fast pass. And it was good not just for the ride we missed but for a bunch of different rides. Instead of going on Winnie the Pooh, I went on Peter Pan later that evening.
Instead of going on SDMT at lunch, I just went on later at night in the dark .. both gave me some fun flexibility for my day with my fast passes.
Same thing happen to me at AK. Had a tough be a bug fastpass (don't ask why) but the ride went down and I got a message that we could use the same fastpass for everest. We got the message just after we got done riding it. Was great to go and just hope right back on again.