I don't think it's a bug as such. You ought to go unconscious at 100%, and won't be able to move if your fatigue/injury/encumbrance penalties sum up to 100% or more.
If, however, whatever caused the 100%+ injuries doesn't proceed to kill you it ought to be possible to heal and wake up, but if that was the case you'd have to have been unconscious for a day (past the next morning day turn over), in which case you'd be very hungry and very thirsty.
Are you sure it was the injuries that were over 100%, rather than the total penalties? It's certainly possible to have penalties above 100% and thus be unable to move, but still remain conscious (for a little while). If you wake up with 86% injuries that ought to be what you received, with the remainder stemming from encumbrance (some of which the robbers probably relieved you of) and fatigue (you probably fought them).