I woke up this morning to this:
Our robin's nest turned asunder, and initially, no babies to be found
I did eventually find two of the three babies, and thinking they were dead, tried to scoop them up very gently. Turns out, they were both still alive, barely, so I righted the nest and (never touching them, because I don't know if it's a myth or not) tucked them both back in, hoping beyond hope that their mom would show up.
She has. She's been in the nest with them since I put them back in.
Fingers crossed and good vibes...