Hi Paul. It looks like the spray adhesive was wet when mounting your pattern. Either that or you sprayed the adhesive directly to the wood. Each spray adhesive is different, so I'd read the back of the can for instructions on temporary bonds. But usually what you do is spray the back of the pattern and let it sit for 20-30 seconds or so. It will be tacky like a post-it note. Then apply to the wood. Don't spray the wood directly. The grains will soak up the glue and you'll have a mess on your hands.
If you do it like this, the pattern should remove pretty easily. If it doesn't, use some Mineral Spirits and wet the paper pattern (I use a paper towel to apply the MS). The paper will turn translucent. Give it a couple of minutes, then try removing. It should slide right off.
As far as fixing the problem, try soaking the top with Mineral Spirits to loosen up the glue and gunk. Let it sit for a few minutes and try wiping it off with a paper towel. Do this a few times and set it aside to dry and see the results. If it looks better, I'd either repeat the process or switch to sanding. But the main goal is to get the glue removed before sanding. Otherwise you're just smearing the glue and sawdust into a mess.
I hope that works for you. Keep us up to date.