Slug in potted plants ordered online

The major disadvantage of ordering plants online is that some dangerous pests can be included in the pots which can damage the existing plants . For example an insulin plant was ordered online, and was despatched in a black bag .
However when the black grow bag was slit it was found that there is a very big brown, black slug in the mud of the pot and it was trying to get out. It was not easy to get rid of the slug, only covering with wet newspapers ensured that the slug did not roam around and cause damage to the other plants in the area. So if it possible, it is always advisable to grow plants from seeds, instead of importing pests from other places.