Thank you for your question. Please do not feel that your question is a dumb one. It is a valid question which I hope to answer effectively.
I have only seen snippets of Futurama at best but I have heard of that episode. In regard to what is possible in reality, there are actually many cases where a dog will wait for an owner's return. One of the most heart-wrenching and commonly discussed cases surround the death of an owner. In some cases, the dog wasn't even around at the time of the death and is oblivious to the fact that his/her owner is never coming back. One of the most famous incidents of such an act was seen in Japan by an Akita named Hachiko (or Hachi). Born in 1923, Hachi was eventually adopted by his owner, a professor that worked in the agriculture department at the University of Tokyo, one year after his birth. The two formed such an attachment over the one year they were in each others company, developing a routine of parting at the railway station during the day, and reconvening in the evening. Alas, one year after gaining Hachi as a companion, his owner suffered a cerebral hemorrhage and died. Despite only being together for such a short amount of time, Hachi remained loyal and waited for his dead master at the railway station everyday for ten additional years before his own death.
As mentioned, this is probably the most sensationalized case and it's inspired the creation of several children's books, two feature films, and as recent as 2015, a bronze statue was created in honor of the loyal dog.
However, this is not the only case that has been documented. In more recent years there have been dozens of reports of dogs waiting for dead owners and they are observed all over the planet. From the frozen wastes of Siberia, to the warm tropics of Bolivia, many dogs wait for their dead owners to return; some at the time of documentation had been waiting five years already. Please let me know if you would like links to the articles and I would be happy to supply them.
As for the case portrayed in Futurama, that also has proven to have occurred before. Just as of March of this year, it has been reported that a dog in New Zealand has taken vigil at the spot where his owner had disappeared. Even after the owner's family had taken the dog into their home, the dog managed to escape and returned to the exact place the owner had vanished.
In summation, yes; it is entirely possible for a dog to wait for its owner's return whether the person be deceased or simply missing. Truly, this is another way showing how remarkable dogs are and the lengths they are willing to go for their two legged partners. I certainly hope that this helped answer your question and if you would like more information or if you have any additional questions, feel free to ask!