Overcome by sleep

One afternoon (January 7, in case you care) I spoke with Wife on the phone. There had been some discussion this morning whether she would pick up Son 1 from school, for a variety of reasons. And I called to ask if she felt up to it or not.

In the course of her answer, she mentioned that she had been late getting Son 2 because she had fallen asleep during the afternoon and didn't wake up in time. That sounds unexceptionable as a story, ... except that 15 minutes before he was due to be picked up she was IM-ing me. And at that moment she signed off saying "I have to go get Son 2 now." So how was it POSSIBLE that she could have slept through his pickup?

Her answer was that after she signed off of IM with me, she went into the bedroom to get dressed (because apparently she hadn't gotten dressed yet). Once there, she took off her robe (or whatever) and lay down on the bed ... AT WHICH POINT she fell asleep for an hour.

So should I have been frustrated, irritated, ... or alarmed? I formulated questions in my mind like "Why would you lie down when you know you have to leave right away?" "Why weren't you dressed yet at 2:30 in the afternoon?" "Were you really overcome by sleep THAT FAST or did you somehow forget in the space of 90 seconds that you had to go pick up Son 2?" (either option looks bad) And so on. But of course I didn't ask any of them. I just told her, "Don't go get Son 1. Stay home and rest."