El Taino, I think I have a way to fix that for you
first step,,,,,,try to order a replacement set,,,,,,while that is "in the process", try this
it could be a bit of work, but, if that is the only marking you have gotten wet, it might be worth the effort
test it on the black part of the A that tore,,,,,,,,wet that part, and as little of the "main part" that didn't move as possible,,,,nudge it back into place with a microbrush or Q-tip,,,,,,,if that worked for you okay,,,,,,then try the same thing on the larger piece, being very sure you don't leave any of it "dry", and do the nudge thing
let the whole thing dry again,,,,,,,,then cover All the decals on the whole sheet with a coat of Microscale or Superscale decal "Liquid Decal Film" or "Superfilm",,,,,they are both the same stuff,,,,,,you can brush it on, it's self leveling if you don't glop it on,,,,,,2 coats if you have to, etc
let that dry,,,,,,then you can either put the decals on as normal,,,,,,,or if you really have to, you can paint the decal film onto wax paper, and slide your reinforced decals onto the film after it dries,,,,,,,,,,I've never had to do that with any of my "blow outs",,,,,,,,,but, I have read about the wax paper step
as light as Tamiya did those markings, you'll never get an Aftermarket sheet that matches your radome, now,,,,,they are just a bit darker on the AM sheets I have, or have seen
give it a try, because you are going to have a lot of waiting time to waste, and you can always use the Superfilm on any other sheet that you think might have "aged out" on you,,,,,,,heck, I have sheets here that I just go ahead and give a coat to, just in case,,,,,some of them are older than my kids, lol (that means over 30)
good luck
Rex