Cops are now on the hunt for the person who allegedly nabbed Sabrina Ionescu's sneakers from a WNBA arena earlier this week ... telling TMZ Sports they've formally launched an investigation into the allegations.
A spokesperson for the Las Vegas Metropolitan Police Dept. said on Friday it did take a report ... after the New York superstar claimed her Nike kicks were stolen from Michelob ULTRA Arena, where the Liberty had gone up against the Aces twice this week.
So far, no arrests have been made .