usually when you use a tracking dog, you take them to the place last known - that would be where the bikes were laid to rest - but if there is a thought that the bikes might have been put there by a perp, then the last place they were spotted, like in the alley.
I don't believe people really know what the dogs smell when they get a scent and I never have heard anything about what you eat affecting what the dogs sniff - but that doesn't mean it isn't true - nice to ask the dogs if they could talk - there are lots of theories around I suppose and all I know is they get the scent of the missing person and then track it - period. But if the scent is contaminated or the scent item not handled right, as someone else has picked it up then they will track the freshest scent from the item and contamination is a big problem with people that do not understand how to handle shoes and pillow cases - can't just pick them up barehanded.
