There is no reason why the cell phone would have been disposed of, in any scenario. SM rode her bike in an area where there is NO cellular coverage. Carrying a phone would have been extra useless weight.
IF her cell phone is missing, that would tend to be a suspicious clue.
While on the subject of cell phones, there are ONLY two towers that have any coverage on the eastern slope of Monarch Pass. While some seemingly knowledgeable commentators in past Colorado cases have touted that cell phone tracking is infallible..........it is not when there are less than three "pinged" towers. The tower only records the line of sight distance to where the phone is located, at the time of the ping. That becomes an arc of a circle with the center of the circle being the tower, the arc being at the consistent distance from the tower, and the length of the arc being limited by the practical width of the cell. Unless two towers are equal distance from the phone within half of 35 ft, there are going to be two places where two arcs intersect. which could be a very small distance between, or as much as 33-34 miles apart in open country. However, when a third tower is pinged, there is only going to be one place where the three arcs intersect, if the phone is not moving within the coverage. I'm sure all of this is clear as mud to many people, but in practical example, the entire path of KK with Kelsey Berreth's phone and her own, driving more than thirty miles of Interstate highway, taking the turnoff to a deep canyon, taking a little used side road and parking while she tossed personal items into the canyon was traceable by LE; but when PF LE theorized that was driving with that same victim's phone two days earlier, and KK was with him, the three phones could have been together of could have been 30 miles apart. For LE, it only made sense when combined with other evidence to make one of the two locations a logical match to witness testimony, and thus eliminate the other. One Monarch Pass, however, there is only one main road and very narrow cell coverage from the Verizon tower which is in a parallel line to the general path of that road up the east slope. The distance from the tower to the phone is going to fall on the road, which would retain an accuracy circle of 5 meters, or about the width of the two traffic lanes. Bottom line: LE surely has been able to track the movements of SM's phone to and from her home in an automobile for the previous week, but not on her bicycle or on foot. LE would not be able to determine of her phone was "staged" within 2000 feet of her house unless the phone got very near Hwy 50.
As I stated in previous posts, BLM's entire trip to Denver, his movements in that city, and his drive back should have all been verified by now, using cell phone data and traffic cam video. IMO