He appeared to have a small plastic box in his hand and after fiddling with the container he bent down and hid it under a flower box standing on the pavement. He then walked off, talking to somebody on his phone.
Karen Brittain, whose café door is just a few feet from where the container was left on 1 July, was alarmed by the man's behaviour and called the police, who then sealed off the area.
She said: "We were closed down for several hours and it was a disaster for us really, because we had been very busy that morning and it was a beautiful day and we probably would have been very busy."
A unit from the Royal Logistic Corps at Catterick Garrison were called. They moved the planter to expose the box and sent in a robot to carry out a controlled explosion.
Shops in the area were closed for nearly three hours and business owners say they collectively lost thousands of pounds. Afterwards the remains of the plastic box were left scattered across the pavement.
But it was not a bomb, the suspicious device was a geocache.
Geocaching is an internet-based treasure hunt. Here in the UK it has grown in popularity over the last decade and tens of thousands of people are involved.
The concept is a simple one. Geocachers leave a container, which can vary greatly in size, at a location of their choice. They then put the exact co-ordinates of their box on the geocache website.
Other geocachers then go hunting for the box. There are currently thousands of caches hidden across Britain.
They are found by using a device fitted with GPS - Global Positioning System. The geocacher who has hidden a box puts the GPS co-ordinates online and these are used by other geocachers to find it.
The cache is nearly always well hidden and can take a bit of cunning to find. It's all part of the challenge, but it's also why the centre of Wetherby was brought to a standstill.
The events in West Yorkshire have now made the police and the geocaching community pause for thought. Some online forums are now questioning whether caches should be left in urban areas.
Ch Insp Mick Hunter West Yorkshire Police
In placing the caches, what I would say is, please apply some common sense to where you put them”
Ch Insp Mick Hunter, who was in charge of the response last Friday, said: "Police don't want to spoil people's fun and if people want to geocache then that's great.
"But in placing the caches, what I would say is, please apply some common sense to where you put them."
He also questions putting caches in urban areas.
"If you feel as though you have to do that, then perhaps contact the police, let us know where it is, give us a description and perhaps a picture and a contact number would be very useful."
But what do geocachers think? Dave Palmer, a prolific geocacher, believes there is still a problem with many people being unaware of the activity.
"We still need to get the information out to police officers. Maybe we need to get to chief police officer level and get the information disseminated down to a forcewide level in each area," he said.
Although this appears to be an episode executed in good faith from all sides, it left traders in a busy town out of pocket and the last geocacher to find the box outside Karen's café with a police caution.
And with so many caches around the UK at the moment, will this be the last time one of them cause a bomb scare?