You can't see the HUD on your screen, but you or your owner can still operate it.

Probably you rewore it at a position that 's different from the default, and it went out of the screen boundaries.

Try re-wearing it at "HUD Top Left", which is the default.

If that doesn't work, do this:

1. Rightclick any other HUD you have onscreen. If you don't have any, just create a box, and wear that at any HUD location (e.g. HUD center).
2. Select "Edit" on the Pie Menu.You will see the Red, Green and Blue edit lines.
3. Now, zoom out. If you're on a PC, rotate your mouse scroll wheel. You will see the normal screen boundary limits as a white rectangle.
4. Look for the LULU HUD outside of this white rectangle. If it's not there, zoom out further till you find it.
5. Now, right-click the LULU HUD and select "Edit" on the Pie Menu.
6. Move your mouse over the relevant Red, Green or Blue adjustment arrows and then click (hold it there) and slide the HUD back into the white rectangle (normal screen boundary).
7. Zoom out. Verify all is ok, then detach the HUD (to save its new location). Wait half a minute before re-wearing it again, to ensure SL had saved your new settings.