Although the record of the game itself, does not confirm the move 'glitch' in question, {probably, because I resigned, rather than try to 'play on,' in an illegal position}; in the game, "zugzwang"-"Xindak" {'GMT' 12:59, in the "results" pages}; My very last {16th?} move, {not shown}, as 'white,' was, cxb7; Yet, on my screen; My pawn, capturing on the 'b7' square, ended up on 'b8'{?!}.
 
Since I immediately resigned, {which would explain, the absence of that erroneous, confirming move}; Would it have done any good, had I 'clicked' on the 'backpage' icon?.. I think I already know the answer, since it shouldn't have happened, in the first place!-