The contributor does not recall where she heard this one, but it’s certainly worthy of a post. This is a mashup of “they sold me down the river” (betray) and “up a creek without a paddle” (having difficulty or being in a difficult position). Creeks and rivers seem to be the culprit here. Not sure what the speaker intended here, as this is an incongruent conflation (mixing of two phrases with different meanings). I posted an earlier malaphor that is similar and is a congruent conflation (mix of two phrases with the same or similar meaning): “Up a tree without a paddle”. https://malaphors.com/2012/09/26/up-a-tree-without-a-paddle/
Interestingly, the expression “sold down the river” dates from the mid- 1800s, and alludes to slaves being sold down the Mississippi River to work as laborers on cotton plantations. Its figurative use dates from the late 1800s.
A big thanks to Jennifer Diello for hearing this one and passing it on.