Meta E5 | Phone screen

I was striaght up asked https://leetcode.com/problems/multiply-strings/description/

Unfortunately I hadn't done this problem before :(
Please correct me if I'm wrong, but usually interviewers guide you a bit and let you know if you're on the right track? But this interviewer did not involve himself.
Ocassionaly I would say, "Does this make sense? Would you like me to explain that further? Does this seem like the right approach? Am I on the right track?"
And he always enthusiastically said "yeah yeah! This is good." So, I felt like I was doing great.
I even did a dry run through my code.
After the interview I looked into my solution further and realized I forgot to handle 1 or 2 things. I don't know if he didnt catch them either or if he just didn't want to help :(

Also, I was only asked this 1 question. During the interview I asked the interviewer if he would like me to try more test cases or if we should move onto the next question for sake of time. He said that he only prepared one question. Sometimes he prepares two but this question is multi-step so he felt just 1 is fine in this case. I don't know if that's true or if he just said that.

Nonetheless, it was a good effort. Thanks everyone who gives to the community. Hopefully this helps someone.