HUD Issues
HUDs Not Showing
A HUD's orientation data (position and rotation) data is stored with the HUD when it's detached. It is relative to the attach point, not to the viewer. (Any attached object has its orientation data saved when it's detached)
HUDs Are Not Working
There is what appears to be a server-side bug: BUG-41379, which can cause all scripts in the region to switch to the Stop Running state. Unfortunately, this is a rather permanent breakage if you don't have permissions to start/run/reset scripts on the object.
Note: While this issue most commonly affects HUDs, it can also affect any and all other scripted attachments you were wearing when the breakage happened.
There are a few things you can try to get the items working again.