In his first appearance in the elite inter-club championship for his new side, the 23-year-old was forced to take an early shower, his side mounting a late fight to grab a 2-2 stalemate at Parc Olympique Lyonnais.
Adams picked up his first of two yellow cards in the 18th minute for fouling France attacker Nabil Fekir, who broke the deadlock just a minute later.
Tanguy Ndombele then added a second goal in the 28th minute before Adams was brandished a second yellow card six minutes after the break.
There was more misery for Hoffenheim as Florian Grillitsch was forced off the pitch by injury six minutes later.
The German side, however, fought back strongly to register a consolation through Andrej Kramaric in the 65th minute.
And when all looked headed for a 2-1 score, Pavel Kaderabek scored two minutes into injury time to snatch a hard fought 2-2 draw on away soil.
The point sees Hoffenheim third in Group F, three and six points behind second-placed Lyon and leaders Manchester City respectively.
Adams, by Wednesday's development, will miss the penultimate group game against Shakhtar Donetsk later this month.