I think this is totally wrong. When you have both parties speaking multiple languages this happens all the time. You see this more with English being the loaner more often than it is the borrower, due to the reach that the language has. Listen to an Indian or Filipino speak for a while, it's interspersed with English words ALL the time. It happens less in English as there is not the universal knowledge base of one specific other language, but it does happen sometimes when searching for a certain, je ne sais pas.