[Edited because this is a non-issue.]

[No spoilers]
Side Quest: Til Death Do You Part

̶I̶n̶ ̶t̶h̶i̶s̶ ̶s̶i̶d̶e̶ ̶q̶u̶e̶s̶t̶,̶ ̶i̶n̶ ̶T̶o̶u̶s̶s̶a̶i̶n̶t̶,̶ ̶y̶o̶u̶ ̶h̶a̶v̶e̶ ̶a̶n̶ ̶o̶p̶p̶o̶r̶t̶u̶n̶i̶t̶y̶ ̶(̶i̶f̶ ̶y̶o̶u̶ ̶p̶i̶c̶k̶ ̶t̶h̶e̶ ̶r̶i̶g̶h̶t̶ ̶a̶c̶t̶i̶o̶n̶)̶ ̶t̶o̶ ̶g̶a̶i̶n̶ ̶*̶s̶o̶m̶e̶*̶ ̶g̶w̶e̶n̶t̶ ̶c̶a̶r̶d̶s̶ ̶-̶-̶ ̶i̶t̶ ̶i̶s̶ ̶n̶o̶t̶ ̶s̶p̶e̶c̶i̶f̶i̶e̶d̶ ̶h̶o̶w̶ ̶m̶a̶n̶y̶.̶ ̶T̶h̶e̶ ̶c̶a̶r̶d̶s̶ ̶a̶r̶e̶ ̶s̶u̶p̶p̶o̶s̶e̶d̶l̶y̶ ̶g̶a̶i̶n̶e̶d̶ ̶a̶f̶t̶e̶r̶ ̶a̶ ̶f̶i̶g̶h̶t̶ ̶a̶t̶ ̶t̶h̶e̶ ̶e̶n̶d̶ ̶o̶f̶ ̶t̶h̶e̶ ̶q̶u̶e̶s̶t̶:̶ ̶G̶e̶r̶a̶l̶t̶ ̶b̶e̶n̶d̶s̶ ̶d̶o̶w̶n̶ ̶t̶o̶ ̶p̶i̶c̶k̶ ̶t̶h̶e̶m̶ ̶u̶p̶,̶ ̶c̶o̶m̶m̶e̶n̶t̶s̶ ̶o̶n̶ ̶h̶o̶w̶ ̶h̶a̶p̶p̶y̶ ̶h̶e̶ ̶i̶s̶ ̶e̶t̶c̶.̶,̶ ̶b̶u̶t̶ ̶t̶h̶e̶ ̶c̶a̶r̶d̶s̶ ̶a̶r̶e̶ ̶n̶e̶v̶e̶r̶ ̶g̶i̶v̶e̶n̶ ̶t̶o̶ ̶t̶h̶e̶ ̶p̶l̶a̶y̶e̶r̶.̶ ̶A̶n̶y̶b̶o̶d̶y̶ ̶e̶l̶s̶e̶ ̶c̶o̶m̶e̶ ̶a̶c̶r̶o̶s̶s̶ ̶t̶h̶i̶s̶?̶ ̶M̶y̶ ̶G̶w̶e̶n̶t̶ ̶c̶o̶l̶l̶e̶c̶t̶i̶n̶g̶ ̶h̶a̶s̶ ̶j̶u̶s̶t̶ ̶g̶o̶n̶e̶ ̶o̶n̶ ̶t̶h̶e̶ ̶b̶a̶c̶k̶ ̶b̶u̶r̶n̶e̶r̶.̶ ̶G̶r̶r̶r̶!̶

Turns out that the cards in this quest are NOT Skellige deck cards, so if you already have them you get nothing.
Though it would have been nice for Geralt to have not remarked in such a case.

[Edited, non issue.]

Yep I have this issue as well.

Happens to me too... At first I thought I bugged it because he bent down and picked them up mid fight. But still happens after reload. No cards

Same thing happened to me, I thought maybe I had those cards already but I guess not.

I just decided to reload and put that quest on hold.

[Edited, non-issue.]

See my initial post. This is a non-issue.