LONDON — Memories of a brand new bicycle — and the mystery man who gave it to her when she was a 5-year-old in a Dutch refugee center — have played out as vignettes in Mevan Babakar’s mind for most of her life.

Ms. Babakar, now 29, said the generous gift from a man whose name she couldn’t remember had shaped her childhood. On Tuesday, she suddenly found herself reunited with the man whose face had flickered through her memories for more than two decades.

And it all began on Twitter.

“I was a refugee for 5 yrs in the 90s and this man, who worked at a refugee camp near Zwolle in the Netherlands, out of the kindness of his own heart bought me a bike. My five year old heart exploded with joy,” Ms. Babakar wrote in a post on Twitter, before pleading with the internet to help her track him down.