How do you keep track of a cell phone?

Thank you so much, I am new to this group and I have found a lot of useful information

If it's an android cell you can use "find my phone" function provided by google show a location on a map and to ring the phone. I set the phone to light up when it rings because I often find it easier to see the light than hear the ring if the phone has fallen between cushions on the couch or in bed covers.

Can you invest in a landline for these calls?

Canservive, easy, go back to using landlines. I refused to give up my landlines because if there is an emergency issue where I am unable to talk, the emergency dispatcher will see my address automatically on his/her screen. With a cellphone, usually the dispatcher only knows what cell tower the ping is coming from.

My Dad use to lose his portable land-line phone, and he would forget to place said phone back into the carriage to recharge. Dad was just use to the old fashioned landlines.... the phone rings, you pick up the receiver, easy. This type of phone has been ingrained in elder's minds. And corded landlines are never lost. I have a landline phone in just about every room so no hunting for that always missing cellphone [I refuse to wear it on myself due to radiofrequency radiation.].

Thus, you may want to double think about that cellphone for mother-in-law. She can call her friends on an old fashioned phone.

My mom has a small bag/purse like pouch she wears around her neck where she keeps her phone anytime she is walking around the house. When she is in her bedroom/main area where her big table is she has one of those magnetic stands so she can just put the phone on that when plugging it in or not wearing her pouch. There are also things you can put on the phone and maybe even apps that send out a sound when you push a button from a reasonable distance away, kind of like a locate your phone or keys, you could just secure the main calling thing somewhere in the house so it can't move and she always knows where to go to set off the location alarm.