We claim the ornamental design for a loft bed, as shown and described.
FIG. 1 is a perspective view of a loft bed constructed according to the principles of the invention;
FIG. 2 is a top plan view of the embodiment shown in FIG. 1;
FIG. 3 is a front elevational view of the embodiment shown in FIG. 1; and,
FIG. 4 is a left side, elevational view of the embodiment shown in FIG. 1.
The subject matter shown in dashed lines, and any surfaces of the design not shown, including interior surfaces, form no part of the claimed invention.