the only sub in the bay of Biscay at this time was U-52, who operated in BF 50, BF 60 and BF 90.
In the KTB there is no information for the mentioned days, but on June 18, he noticed a Lazarettschiff in BF 5169 at 12h00. He says "it's a pity who knows if there are only wounded persons on board".
Perhaps was it the Wilhelmina?