Didn't hear my baby?

Okay, I need some feedback. I am a first time mom, I had my son 2 months ago. Every night he wakes me up for feedings every 3 hours. My fiancé works every day, so as soon as I hear my son start squirming I jump up to get him before he wakes my fiancé up. My point is- even small movements can wake me from a sleep normally. Last night, I had family staying over, and when I woke up this morning they told me they heard the baby screaming very loud and for a long time during the night around 1am. I don't recall this. Eventually, when I didn't wake up my fiancé got up and rocked the baby back to sleep. At 3 am I remember the baby start moving around in his bed and I woke right up to feed him. And repeated this every few hours like I normally do. I am very upset with myself and a little concerned. I have NEVER slept through his cries. This is the first time it happened and what's even worse is the baby's bed is right next to where I sleep. Less than a foot away from me. So to hear my family say he screamed for a long time (before my fiancé woke up) is scary. I did have 1 glass of wine earlier in the night, and I was very exhausted. But I can't imagine either of those things made me sleep that deeply? I'm always exhausted, and I have drank more other nights and still woke up. Can anyone let me know if it has happened to you?