FugQ Daxter

Is there any documented occasions where we might see someones Yellow dot on a Mini Map, when indeed, they are not truly there? I saw a persons Yellow dot at a place with a person we both know. (no foul play suspected). At a time when this person was supposedly away from her PC and asleep while still logged on. IM's went unanswered when I tried to speak and I was put out by what appeared to be rudeness on her end. I left that location and came back, and both partys were gone. My friend maintains that she was never at her PC at the times I say they happened. She claims it must be a glitch in the system. She is adamant that what I saw cannot have truly occured and is now put out herself because I have made a terrible issue over it. Sorry if this sounds like the makings of a bad soap opera plot but this person is dear to me and this is on the verge of ruining a friendship. Does anyone have any input? Thanks in advance if you do. Thanks