Alt-tabbing out of the game and back can shift character positions, so you could try doing that repeatedly until Elkar reappears. Also, a couple people had some or all of the BF merchants shift position slightly each time they entered the BF, so you could keep exiting and entering the BF.
You can also reset NPCs' positions
Teleporting anywhere (via hex editor)It doesn't look like there is a patch for the Polish version of BD, but if you were playing the English version, the
patch changes the BF merchants' inventories so they are regenerated each time you enter the BF.