She was upset bless her!
We had originally put her dummies into a Tupperware pot and covered it with Christmas stickers. It just so happened that on her 3rd birthday, Santa was coming to nursery, so we gave them to him to give to all the new babies as presents. That first night was hard, but she seemed to feel ok when we reminded her about the new babies getting dummies from Santa. She did really well after that first night, and stopped looking for the dummy after about 3 nights.
The shopping incident was about 2 months later. When I discovered her stash, I felt such mixed emotions, fear at being locked up forever due to theft, (irrational as I also had a new baby and was all hormonal) pride at her ingenuity, and worried that she was more upset at giving up the dummies than we had realised.
I also had the conundrum of what to do with the stolen dummies in that moment, ie take both children back out of the car and traipse back to the shop to confess I had given birth to a thief, or just leg it. Dd's tears made me quickly realise that the best option for my sanity was to leg it. I distracted DD in that moment with some food treat from the shopping and discreetly hid the dummies.
Once home, as DD went to do something I would point out that only big girls can do whatever it was she wanted to do, eg glueing, sticking etc. So things like, "it's a good job you're a big girl cos only big girls can do X, babies can't do X." Then at bedtime when the pleas started for the dummies I asked her if she didn't want to do X anymore cos only big girls can do X, and only babies have dummies.
Once we got past that first night, she was fine again. I can't even remember what I did with the stolen dummies.
She's a tall teenager now, thankfully few of the stereotypical teenage traits. No more stealing (that I know of!) Sport mad, but still easily distracted with food treats. 