Toilets clog for a number of reasons, generally due to what is tossed into them. If a toilet has been clogged on purpose, you may be able to tell when you finally remove and identify the clog. If the cause is foreign material that normally doesn't belong in a toilet or there is a lot of what is typically found in a toilet, the odds are that it was done on purpose.
If you find that an object that should otherwise never be inside a bathroom, let alone inside a toilet drain, was causing the clog, it is more than likely that the object was intentionally placed inside the toilet and flushed. This includes kitchen utensils or items normally found in other rooms. If the object is typically found inside a bathroom, such as a hair brush, it could have been accidentally knocked or dropped into the toilet.
Excessive tissue is a possible sign of a purposefully-clogged toilet. Especially if only adults, and no small children, are using a toilet, someone who tosses handful after handful of toilet tissue inside a toilet drain is almost definitely trying to clog it. Even though the toilet is designed to handle tissue along with the waste and water, too much tissue will easily clump together and block the drain.
If there is a small child inside the home, the possibility increases that natural curiosity or mischievousness led the child to toss something into the toilet and flush it away, intrigued by how the toilet operates. If you extend the cable of an auger through a toilet trapway and pull back a small toy that was flushed down, the case is basically closed. As innocent as a child may be in not having intentions to cause a clog, flushing a toy or even excessive tissue or other foreign objects down a toilet is often done on purpose.
Often, when a toilet is initially clogged, the water may rise inside the bowl, but it will not overflow. That is, until it is flushed repeatedly. If the toilet has overflowed due to constant flushing, it is likely that someone intentionally clogged the toilet or, at the very least, intentionally kept flushing it to create a flooded bathroom floor.