It was User:pdf23ds. Here's the note. Excerpt:
I wish I could have been cryonically preserved. But suicides aren’t treated well enough for that. We get sectioned. I tried asking the cryonics places about options, but they wouldn’t talk to me. Fuck you, Alcor. Fuck you, CI. I might have lived except for you.
This post was from awhile ago and I don't think anyone with access to the note is still around to supply it. You could try asking everyone here for a copy and see if anything comes of it.
Thanks. If anyone has a copy of the letter, please send me a private message.