Thanks to all who helped me by providing links and information. I have been researching further. From army records, I believe my grandfather was in Pionier Bataillon 741 (feldpostnummer 40276) which was part of 11th Army. His sons tell me that he would write home describing the awful situation he and his fellow soldiers found themselves in, with the numbers in his unit diminishing rapidly and writing of a retreat and heading towards Hungary.
After reading up on the decimation of the Germans in Romania these comments make sense. I need some clarification though and perhaps someone could help me?
I understand most of the battles in Romania were over by early September 1944 and that all 14 German Divisions were destroyed, though some were later rebuilt. I think something like 98 000 German prisoners were taken, my grandfather amongst them - I think. You see his wife was sent a letter stating that her husband had died on 13 March, 1945, but I have found that he actually died in December 1945 as a POW in Focsani. Can anyone enlighten me on might have happened here? Is it possible that amidst all the chaos of retreating Germans, men dying and being captured that he may have been captured in March and no one in higher authority knowing his whereabouts? Or, were there other events that happened after March in or around Focsani that he may have been involved with before being captured? It is just that there is this gap of time between September 1944 and March 1945 when I can't find out where he was.
Also, is it possible to find out how to obtain information about the POW camp? Who would hold such records?