LOL agreed, It sounds like they werent glued in the first place. Dont ask why I say that LOL. Yup I did the same in that duplex I built. A lot of connections to glue. Missing one for me was pretty good .....
I never heard of waiting 2 days for glue to set. If proper glue and primer was used to start with , it would be ready in 5 minutes. That line is not under pressure, just gravity. It almost sounds like one of the pipes was cut 2" short to start with also
Glad you found it. What a pain!!