> What would be suspicious is being in possession of the one-time pad needed to decode the messages

Would it though?

All you need is something with sufficient entropy. I reckon you could do a "good enough" job with any plausible-looking data you have lying around on your hard disk right now. Say for example if you took a couple of sha256s of any random image you might post on social media, you'd have quite a lot of key right there.