The wood grain you speak of is called a "Photo Finish" and sometimes repairable, sometimes not....depends on how badly the finish is damaged.
It is simply an image of woodgrain printed om a thin film of paper material that is adhered to the wood underlayment of a cabinet. As you discovered, sanding it simply damages the finish even further.
Repairs are usually made by hand-painting the wood grain over damaged areas....takes a bit of skill obviously.
Googling "Radio Photo Finish Repair" will turn up lots of hits to help you decide what path to take.
CLICK HERE for an example of but one project.
Good luck. I myself intentionally avoid those photo finish radios. Too many headaches.....but if you enjoy a challenge.........
This is basically a woodgrain decal- a wood design photoprinted onto a thin paper or celluloid-like backing which is then adhered to the cabinet. It is surprising that it didn't melt when you stripped the cabinet. I'm guessing that you have the paper variety- the celluloid kind turns to goo when stripper hits it.
You can buy thin, paper-backed real wood veneer in a variety of wood types- even burled walnut, if that suits your taste. After stripping and sanding but before staining, just use 3M spray contact adhesive to bond a razor-cut strip of the thin veneer to your cabinet and proceed with staining/final coating. This approach works very well since you are using real wood; the disadvantage is that it "sits proud" above the rest of the cabinet a small amount- something that I personally don't find objectionable, but it somewhat defeats the illusion of an inlaid wood strip.
I refinished a Motorola 9Y with this approach 25 years ago and it still looks nice.