Past tense confusion

Dear Forum Members:

There is a mistake in the following exchange:

Person A - "Why didn't you answer the the telephone?"

Person B - "Because I had a bath."

I assume that person B should say "Because I was in the bath" or "Because I was taking a bath". Which response is preferable?

Also, WHY is "Because I had a bath" incorrect?

Thank You

[Alc112]

hi!!1
I think "because i had a bath is correct" cuz person A asked in past tense and the person B also had to answer in past.

[Casiopea]

Person A - "Why didn't you answer the the telephone?"
Person B - "Because I had a bath."

I believe the implication is, What were you doing that you didn't answer the phone? Consider:

What did you do?
I had a bath.

What were you doing? Why didn't you answer the phone?
I was in the bath?