Yes, trichomonas often is "dormant", that is causes no symptoms with standard tests negative. It probably can be carried in the vagina for years, and perhaps by men as well. The standard test used by most providers is to simply look at vaginal fluid under the microscope, but that misses many (most?) cases. Ask for a culture test, which is more successful and available in most standard laboratories. However, culture misses many cases as well. Some special labs now offer testing for trich DNA using polymerase chain reaction (PCR), which is the best by far; but it's not yet widely available. There is debate among STD experts about how important it is to routinely start using culture or PCR to detect silent cases. Most trich isn't serious, and prevention doesn't have the same priority as, say, chlamydia or gonorrhea or syphilis.
Good luck-- HHH, MD
Can trich b passed with vibrators and dildos if not cleaned properly?