Can you use Target Whistle on an opponent's discarded Robo Substitute?
Target Whistle says that it can bring back a Basic Pokemon card, but the Robo Substitute in the discard pile is a Trainer card, not a Basic Pokemon.
Source: Phantom Forces FAQ (2014-11-13), TPCi Rules Team (2014-11-13)

Relevant cards

Note: All applicable cards may not be listed below.
XY4_102
XY4_106