it may have been like an anxiety pee... you said it was the longest that you left her.... alos if you are going to leave her during the day i'd really suggest the x-pen... i knwo you said that someone will come to check on her but being a puppy she needs access to water and food... i'd lay down pee pads on the opposite end of where you would put her bed and food and hope she gets the picture
try spending all next weekend teaching her pee pad training. Layla is not pad trained so i'm so sorry but i'm no help with that! good luck! she'll get there