Vegas Nightclub Rats Out Lindsay Lohan

Lindsay Lohan needs to choose her friends ... and her clubs more carefully, cause she just got thrown under the rehab bus.

Lindsay spent what she thought would be a private evening this weekend at Prive nightclub at Planet Hollywood Resort & Casino in Vegas --until the club fired off a gratuitous press release, allegedly exposing her relapse.

In the release, the club buried this item -- "Mel [B] was drinking Merlot and Lindsay asked for a Vodka drink mixed with soda water and a splash of cranberry."

It squarely contradicts Lindsay's outburst last week, when she said "I don't drink...a**hole."

With friends -- and clubs -- like this ...