I posted a list of bugs and issues reported following the 1.11.2 update a short while ago, but this bug is potentially so costly for people that I thought I should make a separate entry for it.
Something has been a bit odd about auto-return since the 1.11 update, because people who own the land have been finding that if they build their prims are returned to them, in a seemingly random way.
Even on land with no auto return, people have reported odd things disappearing or being returned to them, although I hadn't experienced that until this morning. Oclee is building a set for publicity photographs of his fireplace, and needed a chair to put in the corner, of the right shape and elegance to go with a renaissance-style fireplace.
I dragged my Relic inventory box, by Toneless Tomba, from my inventory to the ground. The notecard that is delivered whenever it is rezzed was delivered to me, but the box never appeared. It has gone from my inventory and isn't in my lost and found or my trash. It has vanished off the face of my inventory and the world. It contains a lot of stuff that has sentimental value, things I have been given and have bought, and don't currently have out in my house.
I even removed the surface patch in case I had accidentally buried it. I haven't.
My advice is, don't rezz anything expensive, or any storage device for things you don't have copies of, really, don't rezz anything that isn't copyable, until they have fixed this. As people are reporting that vendors and buying are not delivering goods to them, maybe it would be sensible not to buy anything too expensive either?
Update: arrived about 20 minutes later, about 100 metres from where I rezzed it. Weird.