Noel Joel had packed his favourite sweets and left without warning while his mother thought he was playing in his bedroom.
After noticing her son and his bike was gone, Joel's mother frantically alerted the police.
He was stopped after three miles when police received reports of a confused small child traversing the road multiple times, German Herald reports.
The officer said: "He didn't really know the way to the hospital. But he blamed that on his bike for not being fitted with sat nav."
A family friend explained: "He is a very determined, confident little boy.
"He was worried about his grandmother and wanted to do something about it."
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