In the TNG episode "Schisms", Enterprise crew members are taken against their will (and without their knowledge, at least initially) to a subspace realm where they are experimented on by solanogen-based lifeforms (pictured below, screenshot care of Memory Alpha). For instance, Riker has his forearm detached and then re-attached. Another crew member's bodily fluids are replaced with a polymer-based substance, leading to his demise.
At the end of the episode, the aliens launch a kind of probe from their realm into normal space. Shortly after, the senior officers speculate a bit about the probe — whether it was launched just for exploration or whether it was part of further hostilities by the creatures.
According to the Memory Alpha article for the episode (linked above), senior production staff were unhappy with the aliens' look and decided to abandon this open storyline. That being said, they may have had an idea of where to take the story.
Is there any record (from interviews, etc.) of any intention for the probe in future episode(s)? Perhaps more likely: are there any references in the Extended Universe to these creatures and specifically to their probe?