Hi!
Normally when you do Zoom/E (Just learned recently ZE works as well as ZS!) there is a hidden layer, something locked or hidden. I thought this was also the case now but just in case I took an item, copy and pasted it into a new document. All layers are visible, no layers are locked, nothing is hidden, yet something is very very far away.
just lock everything you can see and select by picking. Then use CTRL+A or _SelAll and the commandline should report what has been added to the selection. If you use ZS and the camera changes but you see nothing, press delete to get rid of it.