I ran into an odd situation at work today which we still have yet to figure out how they accomplished the feat;

Two side-by-side closets were wed into one big space. Each set of can lights were operated from a different hot feed, one for each room. We figure at some point the single pole switches were replaced with 3 ways, but the hot feeds remained the same.

There are NO wires from the right set of cans to the left set of cans.

When the power was killed to the right side of the closet, the 3-way switches operated normally, with the left side cans turned on and off as usual. The right side cans never lit. Switch position didn't matter. When power was restored to the right side, the switches and cans all worked normally.

I keep a diagram in my electrical supply box with the 3 variations on wiring 3-way switches, but each diagram has only one feed and one load.

How did they manage to have 2 feeds on one set of 3-way switches ?