Paris Hilton lost track of sister Nicky after getting swarmed at the Grove in Los Angeles last night.

While leaving the movie theaters -- where the Hilton sisters apparently saw Michael Moore's astounding health care docu "Sicko" -- photos quickly engulfed the ex-convict as Nicky ran for cover. Paris briefly posed for photos as Nicky disappeared in front of the herd, with Paris stopping to ask, "Where is my sister?"

When Paris finally tracked her down -- Nicky was ready with their getaway vehicle, honking her horn at paps to get them outta her way. That's what sisters are for!