Can I use Junk Arm, discarding something + 1 Item card to get that 1 Item card back into my hand?
No, you cannot return cards to your hand that you used to pay this card's cost.
Source: PUI Rules Team (2011-11-03), TPCi Rules Team (2013-02-07)

Relevant cards

Note: All applicable cards may not be listed below.
HGSS4_87