Which version of the mod do you have, and do you remember what date you downloaded it? I'll go get on my computer here in a few minutes, and post back in here with what I have for the vessel...
Edit: OK, folder and file construction looks fine on my FotRSU v0.063. There are no TGA files for a lot of the ships. Quite a bit of FotRSU has been "converted" to DDS (an SH4 thingie), and the TGA files deleted to reduce the Mod's size. The DDS files do load from the TGA calls in the Roster folders for vessels. You should find an NPL_RC.dds file that looks like this:
It is called with TextureName=Data / Sea / NPL_RC / NPL_RC_T01.tga from the Roster cfg file, but the dds loads.
In the museum, it should look like this:
One thing to remember about the three Red Cross ships in FotRSU is that they are of "Red Cross" nationality, not American or Japan or British.