Yes. Ships in other areas of the map, where web mine fields are visible, generated the usual reports on distance to mine sweep range and number of enemy mines.
However, the ships that reported web mine hits did not report the field (which also does not appear on the map). They only reported hitting web mines. These ships were stopped, drained, and damaged - the only evidence of a field.
Duis digrissim ipsum in rana unicornis!