This is funny! Maybe more of a cultural thing than a language thing. In the US, they have these long, poorly filmed commercials (called infomercials) which advertise a product and give you a number to call to immediately purchase that product. Usually these are weird kinds of inventions--special towels that can dry anything immediately, special pots that never require cleaning--that you can't buy in normal stores. These infomercials are usually on late at night or in the middle of the day.
Similarly, American TV has entire channels of infomercials (called "shopping channels") with long, live shopping shows where they try to sell you skin care, jewelry, supplements, etc. You just "call the number on your screen" to purchase. So, when people say "I ordered it from the TV," they are usually referring to calling one of these numbers from an infomercial or shopping channel and buying a product that way.
Edited to say: You wouldn't say "I ordered it from TV," even though you do say "I saw it on TV," and "Look, the man from TV!" For some reason, in English you do have to put the definite article in there for "I ordered it from the TV." Hope that's a little helpful! Maybe someone else can provide better reasoning for this.