Nicu staff negligent?

My husband and I came into our daughter’s room this afternoon to see that our daughters fio2 was 74%. She’s normally at 32-34% so immediately we panicked and assumed she had some event. Keep in mind we are so close to being home. She has a trach and we are just waiting for her home vent to arrive. We looked around for our nurse and nobody knew where she was. Turns out she was at lunch and comes in and introduces herself. We ask about the vent and she had no idea it was at 74%. We asked her to check the log on the vent and it said her fio2 was at 97% and then 74% since 5:30am. It was 1:30pm when we got in today meaning her vent was this high for 8 hours unnoticed by her night and day RN, night and day RT and during rounds. We asked our nurse today if the night nurse charted anything and she said no. My daughter is still at risk for ROP. I’m just so annoyed by this. We asked to talk to the charge nurse but she’s not come to see us yet. Am I right to be upset about this? Does this happen often?