This is an interesting question. I am guessing that your kuksa was a standard machine turned one with a smooth sanded finish. These feel smooth when first finished but when you get them wet then dry the grain raises leaving it feeling rough. It is a standard problem with any sanded surface and the reason I prefer to leave a tool cut finish.
To keep a good sanded finish you need to get some very fine paper, maybe something like 400 grit and hand sand it lightly. You are not trying to remove all the surface just the rough bits of grain that have raised. Now wet it and let it dry again and sand lightly again. Then oil it. I did a blog post about the pros and cons of different oils here.
http://greenwood-carving.blogspot.com/2009/12/what-is-best-oil-for-treating-wood.html
Then whilst it is still wet with the oil sand lightly, this will only work if there is plenty of oil, just a little oil and the paper will all clog up. Finally wipe off the excess oil. Once this is dried it should not go rough again.