How can I mark sold out items as 'presale' on customer order confirmations?

[Deathmel0n]

Hey, I am trying to add the line (Presale) to all the sold out itemlines on an order, how can I go about doing that? Our customers regularly miss the text on the website, but they are much better at reading their order confirmations, so I figured marking sold out products there would be helpful.

There's a for-loop that lists all the subtotal_line_items in the order, their quantity and variant if there is one. I tried adding code there to check if the line in question was < 0 on available and add the message, but nothing I tried worked out. What's the proper solution for this? Thanks for any help on the matter.