If the documents were not recorded in the notary contract, you probably won't receive any documents either. If they even exist at all.
Why not?
You are not always immediately enemies just because you have a buyer/seller relationship.
You are allowed to talk to each other, and thus you can simply ask the happy seller if he still has some documents when you forgot these things before the contract. And why should the seller want to withhold these documents?! After three years he will probably still have them, since there is still a warranty.
I was the seller myself, we went out for a nice meal after the contract (buyer pays as usual ;)), and I gave all the manuals etc. that I still had at the handover. Afterwards, a bottle was emptied between the four of us.