I drove it another 30 miles last night without any issues and then stopped at the mechanic's place to have him look at it. It's locked in place, the green clip is not broken and working fine, and the flange on the metal 'L' tube of the filter is holding the fuel line as it should. I hope that was just a fluke (installed by the mechanic incorrectly) and I've got nothing to worry about from now on. I can handle clunks and other minor stuff...but gasoline dripping onto a hot manifold isn't so great. Thanks for your input.