Different case lashs. Beagles can be hard work . They have very determined minds of their own ,like lots of interesting exercise , and often try hard to go off to find their own amusement if they feel like it. Hopefully this pup will have either a contact disc or be microchipped or both and will get home safely. Sounds like her collar will have to go up a notch. It used to surprise me how our dog sometimes seemed to 'breathe his ears in' and slither his head out of his collar when he stopped and I didnt, when the collar seemed pretty well fitted when we set out on the walk.
happened to us once with our bischon frise, we then changed to a harness so she couldn't get out of it, it did the trick as well as not choke the dog when she ran off and the lead reached it's full extension as she was in full sprint.