ANSWER - I have no doubt at all that things go on in the natural world which are not perceived by all of us all the time. My only surprise is that people find this to be in any way out of the ordinary. Most people possess, to some extent or another, a ‘sixth sense’ or an ability to see, sense, hear or feel elements not present in the physical world. So if we take your question at face value and assume you did not overhear a passer by saying “The Judgement” and that there was no actual person standing on the bus then yes it is possible and actually quite likely that you have some degree of clairaudinance.
However I would strongly caution against reading too much into this ability. It is a good gift to have and one that will definitely be of value in your chosen path as a witch. But take care to see it as another tool in your armoury rather than a gift marking you out for special treatment by the Gods. One of the biggest struggles any witch has to contend with is the problem of ego and there is a danger that if you put too much emphasis on these abilities you will overlook your more mundane abilities which will have just as much importance in your craft.
And of course don’t be too quick to jump to conclusions. Always exhaust practical explanations before looking for more complex answers. It is important to be firmly grounded in a common sense view on the world when embarking on the path of a witch.