It's to separate the abbreviation from the grammatical suffix.
laid is the simple past tense and past participle of lay, which is the active verb which means 'to put' something, this is what a person does to produce the result that the keys lay or were lying on the TV, those two are the correct English forms in this case.
lay is not only the infinitive of the active verb, it is also the simple past of the stative verb lie as in 'to rest in a horizontal position' – it's pretty confusing.
It's just how they write "the TV" in Swedish. In Norwegian, it's "TV-en". In Danish, it's "tv'et".
So, now you have an insight into how other languages definitize abbreviations of introduced words. (Plus, Danish decided it should be neuter, while Norwegian made it masculine, and Swedish made it common-gender.)