If the blood is sent for a toxicology screen, it is possible for it to show very small amounts of various drugs including cocaine in the blood stream. Urine testing is another method to test for illicit drug use and is also able to pick up on very small amounts of drugs within the system. The length of time that the drug stays in your system depends on a variety of factors including what the drug is, whether you have taken the drug for a short or long period of time, and the method implied to take the drugs.
If you did not actively use the cocaine, it is unlikely that by being in the same room as other people who are actively using cocaine, that you will have any appreciable amount in your blood stream. Also, if being in the presence of people abusing drugs makes you feel uncomfortable and you are concerned about inadvertently being exposed, avoid situations where you may be put in a situation where you may feel pressured into doing illicit drugs. For more information, please meet with you primary care doctor
and discuss your medical history and based upon your medical exam, further testing or lab work may be warranted.