When Donnelly and Stabler bust the kid "Sticks" Stabler is carrying a sidearm, even though he is on suspension. One would think Donnelly gave him a gun when he gave Stabler a fake badge. Yet when they get to the drug stash house Stabler is suddenly unarmed and Donnelly asks him "hey, you don't got a piece, you gonna be okay?"
The detectives should have immediately known Leon Popov was not the man described by Maldanado's sister as being a regular customer of Angelica. His sister said the man they were looking for had a very distinctive burn mark on the right side of his face, a scar that looked like the state of Florida with a circle around the tip. Popov has no such burn mark, or any kind of scaring on his face.