Holiday,
If you're building Revell Germany's 1/48 kit, you can just e-mail the company (go to their website...I don't remember the URL, but there is a link from the R-M site www.revell-monogram.com) and ask them for the decal sheet. It will take a week or two, but they will send a replacement to you free of charge.
The only thing wrong with that decal set, is the low viz decals vary between black and lt gray low viz colors (I think the NAVY and one or two other decals are black letters). On the real helo (per the pictures in Squadron Signal's H-3 Sea King in Action book) all markings were low viz.