Fusion had been using the aliens, which had been taken out of their packaging and inflated, for promotional purposes elsewhere.
The representative gave the two aliens to Counsell as freebies for personal use. He took one home, intending to give it to a colleague's son, but did not know what happened to the second alien.
The authority said Counsell was "somewhat taken" with the aliens and ordered five more of the $2.60 dolls to sell or give away.
Four of the packaged aliens were bought by Counsell's colleague and a fifth was seen in Counsell's tray at work.
But three days later it was gone from his tray and could not be found.
Repco branch manager Richard White asked what had happened to the missing alien, to which Counsell replied he had been given a free alien by Fusion.
White became concerned he had taken company property without authorisation and payment, and arranged a disciplinary meeting.
At the meeting, Counsell was told he would receive a final warning, following an earlier warning about improperly using his staff discount.
He allegedly told White he was "a f****** liar" and "the whole place is full of f****** liars".
Counsell did not turn up to work again and resigned two weeks later.
He told the authority he had returned to work but none of the other employees spoke to him. He felt shut out and uncomfortable in the "hostile" workplace, and felt it was impossible to continue working at Repco.
Repco said it was happy for Counsell to return to work and denied he was constructively dismissed.
The authority agreed he had not been constitutively dismissed, and rejected his personal grievance claim.