Some of the false positive suppression methods allow complete disabling of diagnostics. As a result, such warnings will not be merely marked as false positives in the analysis report but may never appear there in the first place.
To find out which mechanisms exactly were used to disable diagnostics, you can turn on special messages to be included in the log.
pvs-studio-analyzer analyze ... --cfg source.cpp.PVS-Studio.cfg
With this option enabled, the analyzer will include V012 messages in its output to provide information about the exact spots where diagnostics were turned off. PVS-Studio's IDE plugins support navigation by those spots in the source files and rule configuration files (.pvsconfig). The paths to configuration files storing ignore rules will also be added to the log as V012 messages.