Bolno had a room at the luxurious Setai hotel/condo building on March 30, and Laura Lozano's body was discovered there on March 30. According to a Miami Beach PD report, obtained by TMZ, she was found in the area of the bathtub around 1:22 PM.

Bolno was not there at the time ... police say surveillance video shows him leaving by himself at 4:35 AM. Hotel staffers called Bolno when check-out time came and went, and he told them he'd already left ... but added there was a woman in the room who needed to leave. David paid for several rooms, including Lozano's, and although he was in her room, he visited her there but wasn't staying in it.

According to cops, hotel staffers went to the room and that's when they found Lozano unresponsive. Hotel security did CPR and called the fire department ... when they arrived she was pronounced dead.

Law enforcement sources tell TMZ ... officers did recover an "unknown substance" which they suspect to be narcotics. Police are awaiting the results of toxicology to determine Lozano's cause of death.

As for Bolno ... he told Daily Mail Lozano's death was a "terrible tragedy" and she was staying in his room "because she was recording music the night before. She's a client and she was going to sign a record deal with me. I helped her make music."

Our sources tell us there's evidence Lozano was alive around 8 AM, because she ordered room service.

Bolno was trying to sign Lozano to his L.A.-based management firm, NKSFB, where he is currently a partner. NKSFB bills itself as one of the largest entertainment companies in the nation.

We're told Bolno has been cooperating with police investigating Lozano's death, and he's not considered a person of interest.