Can discharge from the penis be found in a urine lab test?

Discharge is STD: Not unless the urine test was specifically requested to test for gonorrhea and chlamydia.

Sometimes: Depending on when/how much exited with the urination and if getting a "dipstick" test or spun / formal urinalysis (which is more likely to identify it). Absence does not clear you of having an std, but yes, can sometimes id from urinalysis.