'You were pigged'

Solution 1:

Deriving as it does from "Pull-A-Pig", which is described as a "drinking game" by Clare Longrigg in the 26 Aug 1993 issue of The Guardian ("Poison ivy and the wallflowers"), 'she is/was/has been pigged' probably originated sometime historically proximate to that publication.

In brief, "Pull-A-Pig...is a drinking game in which men compete to see who can pick up the ugliest woman" (op. cit.). The 'pig' in question, thus, is a derogatory slang reference to an "unattractive woman". OED describes that sense of 'pig' as "chiefly US"; however, I found no evidence that "Pull-A-Pig" is known in the US, and use of 'pull' in the sense of to "pick up (a partner), esp. for sexual intercourse; to seduce" is described by OED as "Brit. slang".

'Pigged' in the use quoted in the question ("you've been pigged") is likely to have sprung from a play on a slurred pronunciation of 'picked' ("she was picked/pigged"), a slur perhaps thought amusing by the semi-adolescent males who might find such a game appealing. Alternatively, of course, 'pigged' may simply have sprung organically from the linguistic demand to name the objects of the "Pull-A-Pig" 'game'.

The historically parallel and equivalent name of the US drinking 'game' (more appropriately called a crime, viz. "Intentional Infliction of Emotional Distress"), if it existed, might have been, variously, "Dig-A-Dog" (midwest) or "Skin-A-Skank" (east coast), although more broadly "Pick-A-Pig" might have been adopted coast-to-coast.

Solution 2:

Seems like an unusual expression, which means, the Urban Dictionary might be the only source at the moment to explain it. In 2013, a user, awbladerunner, defined it as:

Pull a Pig is a game where a group of guys go out and they win the game by pulling the ugliest looking woman.

And so, to be pigged means to be the victim of the prank. The "winner" is the one who gets the "ugliest" girl, 'pig' presumably being metonymy for 'ugly'.

According to The Sun, the expression was possibly popularized from a dating site called Pull The Pig started in 2014 by Josie Cunningham.

The site was apparently aimed at "average-looking women" though currently the website is blank and says it is being updated.

Solution 3:

The answer presents itself from the definition of the prank as "Pull a Pig". Wherever it originates the use of it can be contracted as it is in the example to mean "You've been pranked": "You've been pigged". Heartbreaking and costly trick to play on anyone.