Pokemon GO trainers have had a busy few weeks, but now that the Colossal Discovery weekend is behind us, it's time to officially start concentrating on striking another blow to Team GO Rocket leadership. The latest Rocket Invasion is here and there's is a companion Special Research storyline for players to work through, as well.

Although the Looming in the Shadows Special Research is available now, some Pokemon GO trainers have noticed that it didn't pop up on their list and there is no message waiting for them with Professor Willow. There's no bug here, but there is a prerequisite that many players may not have noticed.

RELATED: Pokemon GO: Wayfarer Launching Worldwide, But There's A Catch

In order to unlock the Looming in the Shadows Special Research, Pokemon GO trainers must first finish up the A Troubling Situation Special Research. This is the first time a Special Research storyline has a prerequisite like this, so many players are a bit confused about why the new tasks aren't on their list of things to do. Luckily, completing the Looming in the Shadows Special Research shouldn't be too difficult if players act now, while Team Rocket is out and about.

Players who don't have Looming in the Shadows unlocked yet will likely want to take a break from catching the best Unova region Pokemon in the mobile game and finish some tasks. Complete each of the steps of the Troubling Situation Special Research and then after claiming the final reward the new storyline should appear.

As Pokemon GO rolls out more frequent Special Research storylines, it will be interesting to see how frequently this sort of prerequisite mechanic is used in the future. As the list of available special research continues to grow, it makes sense to put some restrictions in place to keep the list of active storylines from growing too long.

Be sure to check back in the near future for more Pokemon GO strategy guides, news, and updates. Until then, good luck out there, trainers!

Pokemon GO is available now in select regions on Android and iOS devices.

MORE: Pokemon GO: What Is The 'A Challenging Development' Special Research?