@Vixey are you sure the litter is an Embassy cigarette packet? I tried checking the screenshot you posted out its from Google street walk 2008 isnt it.. but I cant see it looks like an Embassy cigarette packet.. Do you have a clear shot of it at all?
We know the police initially missed the cigarette butt in CL's car.
We have never been told wether they searched the area on melrosegate bridge where she was seen to be talking to a left handed smoker for a disguarded cigarette butt.
With that in mind did they also miss the opportunity to collect cigarette butts/packets or even discarded chewing gum and litter from the pavements outside of her house these might provide vital clues of people who may have been outside her house on the days leading up to her disappearance or the evening of the 18th and morning of the 19th