I know it's not the same as Harry saving Draco from the Fiendfyre in the Room of Requirement in Deathly Hallows -- Draco's, as JKR puts it¹, "Hi. It's so embarrassing, you saved my life. No one will ever let me forget it" debt. The possible life debt I'm asking about would be subtler than that:
"Well, Draco?" said Lucius Malfoy. He sounded avid. "Is it? Is it Harry Potter?"
"I can’t – I can’t be sure," said Draco. He was keeping his distance from Greyback, and seemed as scared of looking at Harry as Harry was of looking at him.
"Draco, come here, look properly! What do you think?"
Harry saw Draco’s face up close, now, right beside his father’s. They were extraordinarily alike, except that while his father looked beside himself with excitement, Draco’s expression was full of reluctance, even fear.
"I don’t know," he said, and he walked away towards the fireplace where his mother stood watching.
Deathly Hallows - pages 371-372 - UK Hardcover - chapter 23, Malfoy Manor
It would seem that Draco -- while surrounded by his fellow Death Eaters, with his family subjugated and feeling the constant wrath of Voldemort, and clearly scared -- chose not to identify Harry, even though doing so would have been in his and his family's best interest.
Did Draco's actions in any way help save Harry's life when Draco didn't identify Harry to the Death Eaters at Malfoy Manor? I don't have a definitive answer for this -- I see arguments for both positions in canon, for and against Harry owing Draco a life debt. Did Harry owe Draco Malfoy a life debt? Or did the events at Malfoy Manor and the Room of Requirement pretty much cancel each other out?