"I drew a character who's not supposed to be there for a whole chapter!"
Seriously? That's the best "it's a work emergency that needs you here to help now." excuse the writer could come up with? I can almost forgive manga writers for the crap nonsense excuses they come up with when trying to pretend they know how things go in an office or another type of business, but this is the sort of thing that you, the actual writer, pretty much do for a living. Or if you're just the writer and not the artist, then it's something that you have direct access to the people who do this part for a living. Surely you can come up with a more reasonable and convincing explanation than that...
"You've got to come and help! My computer crashed and wiped out all of today's work! And I forgot to back it up this time!"
boom. sensible, realistic, reasonable explanation for her needing immediate and significant help that doesn't make her sound like a total idiot.
But of course, I forget. "being a total idiot" is apparently moe or some nonsense. And we can't have all the lonely nerds going a chapter without swooning over their endearingly clumsy waifu.