I've used it a lot though only twice in that procedure and those were for other bitmaps. The bitmap TileSheet gets freed after the form finishes compiling the tools section, which is when it is last used.
Edit: Here's the start of the procedure, though I doubt it will help solve the problem as there's nothing much there:
SCAR Code:
procedure AssembleMapBitmap;
var
l, x, y, Time, tmpBmp, Buffer: Integer;
pos: TPoint;
begin
Time := GetSystemTime;
Buffer := BitmapFromString(384, 384, '');
FastDrawClear(Buffer, 0);
Writeln('RAWR - ' + GfxFilePath + 'Tiles.bmp');
TileSheet := LoadBitmap(GfxFilePath + 'Tiles.bmp');
And GfxFilePath is a set string that definately points to the right place
Edit2: Fixed it - for some reason photoshop saved it with a hidden file extension so Scar tried to read it and failed - saved it from Fireworks and it works. Best of all, with that done, the basic map editor is now done and working well, even with multiple layers