If you click f-3 and b at same time you can see anyone who has invisibility potion on.
MC-8312
INVISIBLITY CHEAT
Resolved
Duplicate
0
loyd johnson
(Unassigned)
Unconfirmed
Snapshot 13w04a
Retrieved
This was fixed in 12w49a, please check before you report a bug.
I've just tried it myself and it doesn't work on invisible players.
Duplicate of: MC-4069 - Please use the search function to see if your bug has already been submitted.
Currently over 45% of tickets are being closed as duplicate.