Hearing and helping baby in nursery

How do you listen to your baby in the nursery so you know if he wakes up? My baby monitor lost connection in the middle of the night. I didn’t hear him wake up in his nursery. It now tells me that my 3 month son has been crying awake for an hour and I didn’t get him. Now i feel horrible. I am close to tears because he was so upset. He got a bottle and is fine. But I don’t want that to be a thing and he feels like I won’t come. woke up because I set an alarm for an hour before he usually gets up so I always hear him. My husband is a rock when he sleeps and is zero help even when our monitor is on. My son usually wakes up around the same time or I get up for work before him but today he woke up early. Now I am so worried something will happen and I won’t hear him. What do you do? Please help.

*I understand many people keep their baby in their rooms up to a year. However after taking to his pediatrician we decided to move him to his nursery. This isn’t us just being unwilling. I will do everything to take care of him. But him being in his nursery has been better for him for many reasons. We transitioned to that and he has done well.