Law / Bought some pesticide from China to sell it in the UK - Poland's police came - advice? [5]

I ordered some pesticide from china (50 grams) and later tried to sell it on Ebay UK. This substance is considered harmful in UK and so ebay cancelled my listing and sent me an email that I am not allowed to sell it. A few weeks later the Department of Sanitation (Powiatowa Stacja Sanitarno-Epidemiologiczna) came to my house with Police and asked me where this substance is and whether I was trying to sell it. I told them that I flushed it down the toilet after I learned it may be harmful. Now they have taken my laptop and phone to check if I was running some sort of business selling this stuff. I spoke to a lawyer and she told me that this substance is not on any "controlled substances" list in Europe and so I should be okay. However, the lawyer said that getting the laptop back can take up to 3 months. I am very worried and need to make sure that I am not in trouble. What should I do?