Samuel told BBC Sport earlier this year that he did not feel completely healthy until midway through 2025.
He has gone from strength to strength since then, winning four Challenger titles – the second tier of men’s professional tennis – since November.
Now, he must now prepare for the biggest match of his career after overcoming the 185th-ranked Bueno.
The Briton’s instinctive reaction to winning was to place his hands on his head in disbelief as he attempted to process his achievement.
It was a second memorable comeback in as many days, with Samuel having beat Goffin 5-7 6-3 6-3 after toppling American Martin Damm Jr – world number 112 and seeded seventh in qualifying – in the first round.
Samuel has never contested a singles match on the ATP Tour, never mind at a Grand Slam, but will now eagerly wait to learn his French Open first-round opponent as he takes to the sport’s biggest stage.
He could yet be joined by Britain’s world number 237 Felix Gill, who will also bid for a first major singles appearance when he takes on 147th-ranked Frenchman Kyrian Jacquet on Friday.