I'm by no means a master in ArubaOS(so there may be a better way to do this), but the only related information I can think of would be found by running a
#show interface gigabitethernet x/x/x
(26-P12) #show interface gigabitethernet 0/0/0
GE0/0/0 is administratively Up, Link is Up, Line protocol is Up
Hardware is Gigabit Ethernet, Interface is GE0/0/0, Address is 00:0b:86:a8:e9:42
Encapsulation ARPA, Loopback not set
Configured: duplex (Auto), Speed (Auto), FC (Off), Autoneg (On)
Negotiated: duplex (Full), Speed (1 Gbps)
Interface index: 1
MTU 1514 bytes
Link flaps: 19
Flags: Trunk, Trusted
Link status last changed: 1w0d 07:06:54 ago
Last update of counters: 0d 00:00:05 ago
Last clearing of counters: 2w0d 07:00:15 ago
It will list:
Link status last changed: 1w0d 07:06:54 ago
Anything that is currently down (no link) with no 'link status change' in over 4+ weeks is probably safe to assume does not have a device patched in.