Your manager doesn’t need you perfect. They need you to say “I don’t know, but I’ll find out.”

Managers do not need you to know everything; they need you honest about the edges of what you know. Guessing confidently is what creates real problems, because nobody finds out until the mistake has travelled. Saying you will find out and then finding out makes you reliable, which is worth more than looking clever. It also costs almost nothing to say.

Use the whole sentence next time instead of half of it. Admit the gap, say when you will come back, then go and close it. People stop worrying about what you do not know once they watch you handle not knowing.