The most likely reason is I removed you from my contacts. I value keeping things neat and tidy. If I need to reach out to someone, I don’t want to have scroll through a couple of dozen of people that there is no contact relationship with. With that in mind, I remove anyone that hasn’t been in contact with me for at least 3 months. Therefore, if I removed you, then it is likely I hadn’t heard from you in at least 3 months.