School IT revamp.
I literally upgraded (and therefore wiped) every client and server.
Obviously, before this, I took copies of absolutely everything. And did things piecemeal over the summer. And even went to the extent of copying/imaging/removing old client drives before doing so or as I went. People stored stuff in silly folders and something they didn't hit their network profiles and one of the things I was upgrading for was a better version of Windows that handled users profiles on a network in a better fashion, so we were killing that legacy but needed to be sure we'd got everything.
One teacher, upon their return, was subject to a subject audit - the big bods go through their teaching and make sure they're compliant with the curriculum and so on. Strangely, at that point, she claimed she'd lost "everything" (even by her admission, that's a handful of files, but anyway). So I "must have wiped it all when I upgraded". The saga went on for a few days, while I explained that we'd wiped nothing that we didn't have copies of, and provided what I had.
No, apparently those things were still missing. I was obviously stupid and had deleted it all. All her stuff was there. I was causing her stress. She couldn't go through with the audit without those files, etc. etc. etc.
So I reached into my filing cabinet and - stacked among several hundred others - was every hard drive from every computer and every server. Pulled, labelled, stored just for such instances. Yes, the "upgrade" didn't wipe anything at all. Not one byte. I'd put new drives in everything, and pulled the old ones, carefully labelling them with their former location, PC number, and who used that PC. And I know that, because I did the entire upgrade single-handed, so not one computer got upgraded without that happening by myself personally.
Strangely, that drive didn't have her claimed files either... shocking! It was at this point that, having a boss who understood IT, there was some hefty backtracking and she "found" what she was missing, and the saga blew over.
Until a few days later, when she claimed that I was blocking websites and they were critical to her department review. It was odd, because I didn't block anything manually unless asked, it was all auto-categorised. And teachers pretty much got an exemption (their web history is recorded and flagged, but it doesn't block pages for them like it does the kids). I asked her to send me the address. She sent me her department curriculum planning document, which is something that every department keeps and contains all their ideas for teaching, what resources, etc. Obviously, that often now includes a web link or two.
I clicked it. The site was dead. I told her "that's not us, the site is down". She made such a fuss, she went straight to the head and complained that I was blocking things she needed to "do her job", etc. etc. etc.. So I investigated. No DNS resolution for it. I poked around, looked up WHOIS records. The domain had expired TWELVE YEARS prior. No other website had ever sat on its domain. Archive.org provided a lovely timeline of updates, ending promptly at the point of domain expiry all those years prior.
I presented this to the head and there was a ruckus. Because that website was in her curriculum plans for the last 15 years, and it hadn't existed for at least 12 of them. And she insisted that she'd been using it all that time, which was technically impossible. She couldn't provide any evidence that she'd used it, we had years of web logs, the kid's accounts had no traces of anything from it or work like that.
She'd basically dropped herself in it twice, in quick succession, and shown everyone that she hadn't been doing her planning for all the time she'd worked there. There was a huge fuss. I don't know/care what happened because they accepted my evidence, and I left shortly after, but last I heard she was being made the "Head of VLE". The day I left, she asked me what a VLE was (virtual learning environment - a website where teachers post resources, homework, kids log in and grab them and submit them back, teachers comment on them, etc. etc. etc.). "That's like Google, right?!" she asked. Yeah. Just like Google. Bye.