It's your fault for lending money rather than asking for a % of profits (if any) like a normal early investor.
This is common advice because it turns good relationships bad, that manifests as viewing former friends as shysters
I've personally lent money to friends when they needed it, and been paid back once they got stuff sorted out.
Though in my younger days I was far less careful, so lending money did indeed go poorly.
Even in the case you describe, it’s much better to gift it: “if you want or are able to pay me back some day, go for it, but I don’t expect or need it.”