Non comprendre, the individual just survived food stress assumingly from the winter, which would not support the migration. Also look at current Siberia, what would it help to migrate X-hunderd km southwards, wintertemperatures out there are not much higher, if not lower than around the Antarctic coast.Excellent! So, the creature could have easily been migrating northward with no initial food stress.
It may have thought there were greener pastures up ahead since it was spring time and just kept on going. Since it was the warm time of year, there was ample water for it to drink on it's trip. However, eventually it may have gotten sick or stuck or something that led to its demise.
Something else about the mammoth mummies in question, with conserved soft tissues, I discussed this extensively with Dick Mol, there is no formal research to the exact causes but all mummies survived the Holocene Thermal Maximum with summer temperatures much higher than today.
Also all mummies thus far, are somehow associated with nearby water. For instance the Jarkov mammoth had waterplants in it's fur. Hence some speculations are possible about the general cause of death and preservation of these mummies.
BTW I think I have a copy of Mol et al 2006 somewhere. Reading that will help.