This interview in Premier Guitar confirms it 🙂 – http://www.premierguitar.com/Magazine/Issue/2011/Apr/J_Mascis_Unplugged_and_Unfazed_But_Not_Unfuzzed.aspx
“Songs like “Where Are You,” “Can I,” and “What Happened” feature distorted guitar parts. Were they recorded with acoustic or electric guitars?
It’s acoustic through a fuzz pedal.
All of it?
Yeah.
And which fuzz pedal did you use for those parts?
I think a lot of those parts were recorded when I was using a fuzz that Jim Roth, the guitarist in Built to Spill, made. I think it’s a copy of a Tone Bender, although I don’t know which one, MKI or MKII.”