When Seb and Julia are drinking in the bar, the waitress never brings their drinks but they both suddenly have full drinks.
A laser microphone does not need a mirror, it reflects off the front of the glass, which is its primary advantage (it does not require access to a room to listen to it; if you had access you'd plant a bug). In fact, passing the laser through the window in both directions would likely cancel any information from sound wave vibrations.
The police would have conducted a toxicology screening of Thomas' body and discovered that he had been drugged. Even if this was not discovered, Seb and Julia would likely face prosecution. They essentially admit to staging a series of actions which lead to Thomas' apparent suicide. A number of people have been charged, and even convicted, in cases where someone died after they allegedly encouraged them to commit suicide. This case would be more oblique, in that Seb and Julia were not directly urging Thomas to take his own life, but they do publicly admit to orchestrating the series of events which led to that suicide with the full knowledge that it might happen.
Even is Seb and Julia were protected from Pippa suing them, they would not be protected from the reputation consequences of their actions. No art dealer, gallery, museum, magazine, or product line would want their name to be associated with such a wantonly cruel act. While Seb might consider it a crowning artistic achievement, it would be financially and professionally ruinous for him and Julia as they would be unable to find work afterwards.
Seb's printer should have been password protected, but as part of the trap, they left it open.