Absolutely. I can show you no shortage of bad oil reports (from our local Cat distributor, and for some reason, they all get sent to me) on engines from 300 hp to 1000 hp showing contamination with metals, water, and/or other chemicals that on retesting are magically gone.
Sample drawing technique is everything; it's easy to get contamination from outside sources, or accumulated junk in the tank or valve that is loosed by touching it, etc. that then shows up as high concentration in the fluid.
Before doing anything, change the oil and put some hours on it. Then take another sample, using proper collection technique. From there you can make a decision. It's not like you're going to hurt it if you're already of the mindset of tossing it for a replacement. Unless a bad rod knock is indicating imminent catastrophic failure, of course - something to discuss with a knowledgeable mechanic familiar with that power plant. But you may get lucky with a clean(ish) report.