Ah, y'er most welcome deary. Now, by what I mean when I say export is, when ye load the rock/other missing objects in the Object Maker, there be a Save button and Export button right near the name and group name of the object. Saving only saves changes ye 'ave made to the object, exporting, I believe, does that and saves its placement in the group order, exports the group as a whole, and allows others to see it when ye use it and send over the group exported file.
Now, f'er y'er issue, I believe the order of y'er meshes got swapped and FH can no longer locate the file, even though 'tis still in that group. Just upload the mesh in Object Maker and click the Export button on the right, below the names of y'er mesh and object group. If I just be confusin' ye, I can provide ye with some screenies. ;3