What did I do wrong with Pleurothallis mastodon?

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I'd never grown a Pleurothallid before. I got a Pleurothallis mastodon in Andy's Orchids' bare-root sale in January 2016. It had a little sphagnum wrapped around the roots.

I put it into a 1" plastic pot with medium-tightly-packed sphagnum, so it would stand upright, but not extremely tightly packed. The roots were very fine, dry and wiry. I don't know what Pleurothallid roots are supposed to look like.

I set that into a glass-topped terrarium with a jar of water inside to keep the humidity up, and some other plants. I didn't have a hygrometer in there, but it was certainly higher than the rest of the sunroom, which varied from 40%-60%.

It got bright shade. My sunroom had night temperatures between 60-70 F / 15-21C and days between 75-85 F / 24-30C. I watered it well with rain water when I potted it up, and then again when the top was dry. That was about once a week. I planned on not fertilizing until I saw signs of growth, which was never.

It never even attempted to grow. The leaves turned leathery and wrinkled and fell off one after another. When the last leaf fell off I took it out of the pot; I saw no sign of life.

What likely went wrong? Could I have planted it too deeply? That's the only thing I can think of. It was just deep enough to stand up on its own. I don't want to try any more until I have a good idea of what to do differently.