The way that could work, if it was positioned that way, is if he didn't leave it when DM saw him, but when he came down the stairs from killing MM and KG. That point in the home is something of a nexus; he would have had to cross through it a minimum of three times.
Pass one: after entering, likely from the kitchen slider, no blood on his shoes, turning to the right up the stairs
Pass two: coming downstairs, possible blood on his shoes, moving forward up the single step into the front half of the middle floor
Pass three: back down the single step, past DM standing behind her cracked open door, likely blood on his shoes, likely dazzled by the neon combined with his VSS, turning back to the right to go through the kitchen and out the slider to exit.
MOO