I actually had something similar happen to me on a lap quilt I was working on with a kitten I had at the time. I immediately blotted up as much as I could with paper towels and then immediately placed the unfinished piece into a huge bucket filled with hot, hot water and 2-4 cups of Oxyclean (and I don't mean the little scoop it comes with sometimes, I mean taking a bakers dry measuring cup and measuring it out as you would flour).
Then I let it sit that way undisturbed for about 2 hours. After that was done, I carefully placed the sopping wet quilt into a micronet large laundry carrying bag, placed that in a garbage bag and brought it into my laundry room. I then allowed the washer basin to fill up with warm water on the heavy setting and setup the machine with the gentlest cycle of agitation I had. To the water I added 1 Dry Cup of Baking Soda and 1 Cup White Vinegar.
Once that cycle was completed, I did 3 more plain heavy water washing cycles to make sure all the Oxyclean, Baking Soda and Vinegar was out, set it up to drip dry and the end result was brilliant - no stains or smells. I completed the lap quilt and gave it to my grandmother, and she never knew :-D
On a side note, I'm a big advocate of Oxyclean. I used it for everything and its safe. We've used it when moving out of apartments in those RugDoctor Machines you can rent - instead of the chemical solutions you can buy for them and it works great. I use alot and mix it with very hot water and it has taken out the toughest of both pet and regular stains.
I've even used it on fabrics I've gotten to sew/quilt with at the quilt store to restore them and it really works great. Oh and BTW if you've let the Cat Urine seep in and dry, worse that its set in for a few days... then let it sit in the Oxyclean for double the time and it will work wonders along with the baking soda and vinegar to neutralize and remove any additional odors.
Hope these ideas help you out a little. Happy Holidays!
Explosive blessings, abundance and inspiration to you all!
- The Creative Seamstress