Hello,
I have looked for more information concerning the POW camp Hoffnungsthal:
There were 1500 POWs, 187 of them American soldiers when the camp was freed, most of them captured after "Market Garden".
Here you can find a German text with an aerial view of the camp in March 1945, on the roof of one of the buildings you can read "POW". These pages seem to come from a book of a local history association in Rösrath.
There is a memorial exhibition with a model of the camp, photos etc in a chapel near the camp, perhaps I can visit it this year.
This camp is also mentioned in a new book about the Wahner Heide (heathland), I'll try to translate a paragraph:
On 04-11-1945 the first American tanks came from Spich. The camp was already left and marauded. Some few German paratroopers still offered resistance for three days, then the Wahner Heide and the camp were taken without bigger defense.
I will try to get that book I have mentioned and contact the association and the exhibition whether they have lists of the prisoners or other useful information.
Christoph
Edit: Here another link with a photo of the remaining barack today and the Polish Marshal Kerlikov visiting the exhibition.
After reading the timeline I am quiet shure that the camp Hoffnungsthal is the one Mary Durst is looking for. The last link mentions also Italian prisoners.
The monastery in Siegburg is still a monastery (but no hospital), but the last 7 friars will leave this year.