Is it fine answering "I hope it's nothing." instead "I hope it's nothing serious."?

• Is there any misunderstanding at Sam's answer?

• Isn't it infered that Sam means "nothing serious"?

Jenny: "I have to leave the office and go back home at once – something's happened".

Sam: "Oh... I hope it's nothing."

Jenny: "It IS something! Haven't you heard me?"

"I hope it's nothing" sounds perfectly fine to my AE ears, and indeed implies nothing serious, although I'd agree with a previous commenter that "I hope it's nothing serious" sounds more natural in this particular context.

"It's nothing" as a complete statement is more often heard in response to an expression of gratitude or, sometimes, an apology:

A: "Thank you for you help in this matter."
B: "It's nothing."

A: "I'm sorry I messed up your work."
B: "It's nothing. (Don't worry about it.)"