I calmly replied a rough idea gives the police a good place to start.
My mum said something similar to my siblings and I. She didnt care what we were doing or who we were with she just wanted to know a rough idea of when to expect us home and vaguely where we were. That way, if we didnt arrive home when we said we would be back and we had not contacted them in some way to update our ETA, they knew where to start looking for us.
On one memorable occasion when my brother was 14 he had told our parents he was going to the local park with some friends to play football and would be back by 6 for dinner. This was in the early 2000s when phones were just becoming common and my siblings and I had one that was only used when we went out alone. By 6.30 he still wasn't home and he hadn't taken our phone so because my dad knew where my brother was supposed to be he started to walk over to the park.
As he arrived, he saw an ambulance in the car park and a huddle of people in the middle of the grass, and by the time he had reached the group he realised it was my brother being strapped onto a stretcher.
Turns out that after the game most of the boys had gone home but my brother and his best friend had stayed in the park, were messing about climbing the football goalposts and he had fallen and dislocated his knee in a freak accident. Fortunately there was a couple walking their dog who heard my brother's scream, ran over to help and had a phone so immediately called an ambulance but his best friend was so upset and in shock that he couldn't tell the couple anything more than my brother's name and how old he was.
Without the basic information of him being at the park and due home at 6pm, my dad would not have known when my brother was "late" or where to look for him and we may not have known what had happened to my brother for a lot longer and my parents would have been much more worried than they were when, while they knew he was seriously hurt, was at least safe and my dad was with him.