Hal eats the mold — "O. says he can only remember…"
O. says he can only remember (sic) saying something caustic as he limboed a crick out of his back. He says he must have felt a terrible impending anxiety.
Context
The "(sic)" is in the text — Hal, mid-relay, editorially flagging his brother's account of his own remembering as suspect usage. And the second sentence quietly swaps memory for inference: Orin doesn't remember the anxiety, he "must have felt" it — reconstruction wearing recollection's clothes. (Assembly note: don't strip the "(sic)" as apparatus; it's DFW's.)