The other thread (that AAJetMan linked to) definitely has lots more scams.
THe main thing is to not give that receipt to anyone. If you dont know where the taxi stand is, ask the security guards to take you to the prepaid taxi stand.
Some of the security wear plainclothes, some wear police outfits.
This seems to be reported more in BOM and DEL.
In MAA, an escort comes with you right from the minute you get your receipt.
Sorry you had this trouble. I always take pride in telling people that India is pretty safe to travel for foreigners....and then I hear these scams. Such a shame.