i had a similar situation on the clackamas river ten years ago. we were fishing for summers at the top of the minefield. i had a fish on and my buddy went for the net and got it caught in the oar lock. he pulled hard enough to get the net and the oar out(in the water).we netted the fish and discovered we had lost an oar. we managed to get to shore and break a maple branch long enough to use as a temp. we picked/bounced through the minefield and caught up with our oar just before the take out at the bottom of the park.

we should of had a spare!