Pedal sometimes getting stuck
A pedal is made of two major components. 


The pedal body, which is where your foot presses.  This part rotates around the pedal axle once per crank revolution.  It does not rotate with respect to the ground or your foot.
The pedal axle, which supports the body and threads into the crank arm.  The axle does not rotate with respect to the crank arm, but does rotate wrt to the ground and to your foot.
Sundries like bearings or bushings to reduce friction.




This is a modern pedal cutaway to show the axle (sometimes called a spindle or shaft.)  The pedal body should turn freely on the axle with minimal finger pressure.  A good shove of the body should make it spin around from 1 to 10 times.   Modern cheap plasticky pedals may only move a part of a turn.

Your hire bike probably had seized bearings in one pedal, making the body locked to the axle.  The quick fix is to add light lubricant in both sides if possible.  If that doesn't fix it, the hire shop should have quickly swapped out the pedal with a spare.   If they were plastic pedals then sometimes they crack in weird possibly hard to see places, but locking the bearings is a common consequence of damage.

Causes - bikes ridden in the wet/salt/grit/sand and put away dirty.  No bearing system likes dirt.   A good clean and relube can save a lot of pedals, but some are just too-far gone.