Percy realized a little bit later that Argus was monster of sorts, therefore, he'd probably somehow been killed at least once. He decided to check with Annabeth. Annabeth was very willing to explain the myth of Argus, as it didn't revolve around her injuries.
"So here's how it goes; Hera created Argus to guard Io, one of Zeus's many mortal wives, because he could keep half of his eyes open while the other were asleep. Except, Hera had also turned Io into a cow."
"How'd that happen?"
"Hera knew something was up, so Zeus had to turn Io into a cow, but then Hera asked for it as a gift, knowing it was Io. Soon, someone Io knew passed by, so she scratched her name, 'Io', in the dirt and the friend immediately prayed to the gods for help. Hermes was feeling tricky, so he came down to help. He told a story so boring that Argus closed all of his eyes, and fell into an eternal sleep."
"Eternal sleep?"
"Death, Seaweed Brain."
"Oh, so after that…"
"Io got rescued and that's the end."
"Oh, cool, thanks Annabeth!" Percy said as he left, before she could ask any questions.