There are some websites that may help:
peoplefinders.com
peoplelookup.com
zabasearch.com
publicrecordfinder.com
There is usually a fee to use these services.
It is often helpful to provide specific information about where in the world your sister was in 1942, how you became separated from her, what surnames were used, etc. to people in a genealogy group that focuses on your particular ethnic group or country of origin, and ask them your question. This may be done in person where you live or on-line through a forum or discussion area such as may be found in the Usenet newsgroups like alt.genealogy and its progeny