I was editing various objects on my parcel and noticed 2 trees sticking out of my house. I assumed I had edited them there by mistake and took them into inventory. Then I saw some of my cushions half in and half out of the house. I took these into inventory too, but I hadn't used these particular cushions in that house at all AFAIR. On my next door neighbour's parcel I saw 2 metal fence panels - both created by and belonging to me, but that I haven't used for about a month, and another tree (but not one of those I had been editing). They had not been there moments earlier. I took them into inventory and logged out.
When I logged in again the two trees were back in the house, there was a planter with flowers (belonging to me) in my neighbour's parcel, and in another neighbour's parcel, a birdhouse created by and belonging to me. I took the birdhouse back into inventory and there still seemed to be one there, so I took that back too. I later tried rezzing another copy of the birdhouse to find it was now a fountain (also made by me). The edit box showed that it was still called a fountain. I took it back into inventory where it was once more listed as a birdhouse.
I deleted all these items as I had copies, and I thought it was better not to risk using items that had behaved so bizarrely
Finally, after boasting today that I hadn't fallen victim to the inventory bug, I have succumbed (ah, hubris): a mailbox I had ordered on slexchange was successfully delivered to me in-world and I took it into inventory, along with several other slx purchases. When I logged in again, the mailbox was missing, although all the other purchased items that I had taken into inventory without opening or rezzing before logging out were there.
I have reported the the last problem as a bug, but I didn't know whether the first problem was something others had experienced, or just a minor glitch. Everything seems normal now. BTW, I don't allow others to create or edit objects on my parcel, or run scripts.