Am I being unreasonable?

Myself and my husband booked a spa and stay last night as a little break from everything. MIL said she was happy to take care of our baby overnight, which is the first time we’ve both been away from baby overnight. We arrived at 6pm and rang her at 7.15 to see how she was getting on. After a brief chat she was eager to get off the call and said to enjoy the evening so we ended it there. 10pm comes around and we hadn’t heard from her so gave her a message and nothing. Lots of calls and messages from then on but still no reply. 2am and we’ve tried to call and nothing. Same at 4am. I’ve now had about 4 hours sleep and then finally at 8.30am she replies saying they’ve just woke up. Our baby currently wakes up at least 4 times a night at the moment so I know the nights are tough and it’s not like they would have just slept through. I just don’t understand the 13 hours of radio silence on our first night away? For context she’s been very intense since the baby has been born - couldn’t really care less about me when I was pregnant. When I say that others say the baby is starting to look like me, she says nooo all says he looks exactly like her son. We’re both quite surprised how intense she has been and likes to look after him alone, without us. I haven’t got angry re last night but I feel really disappointed that she’s not been more considerate. It doesn’t take much to send the odd message or quick call and I know she would have known we would have appreciated that, even if she was trying not to disturb. Ultimately our night away has not been a pleasant one because of it and I’m just as knackered :(