Can you send the posters with someone you know and have them put them up? You won't be there, but a least your posters will. Poster sessions in my branch of the STEM field are very well attended and popular (usually because there's beer!). It not uncommon at all to see at least a few unattended posters in the mix. No one is really put out.
Chime! I did this at a STEM-heavy conference, and, as it turned out, (1) our posters were next to each other(!) and (2) I knew her work well enough to describe it to folks. She couldn't be there for legit reasons, so I was glad to help. This is a good compromise.