My tiny nuc got robbed out while I dawdled through an inspection — lessons learned

Posting this as a warning to fellow slow inspectors. I have a 3-frame mating nuc from a split, maybe two cups of bees. Yesterday was warm and I spent a good 25 minutes going through it frame by frame taking photos, open feeder cup on top, honey frame leaning against the stand. By the time I closed up there was a cloud of fighting bees at the entrance — robbers from my big production hive next door had found it. This morning the nuc is nearly cleaned out and there are shredded cappings all over the floor. The bees survived and the queen's alive, but the stores are gone. I know it's my fault. What do the experienced folks do differently with nucs — how short is short enough, and do robbing screens actually work once robbing has started?