Concern about possible phone compromise after strangers used my phone

Last night I was approached by three strangers who asked me to make a call for them. I agreed on the condition that I would dial the number myself and hold the phone the entire time. I dialled the number, put it on speaker, and watched the screen continuously.

Because it was hard to hear, they pulled my hand closer to their ear so their hand was touching the phone while my hand was still holding it. Two calls were made, then they left for a few minutes (they did not take the phone with them) and returned to make another call. To the best of my knowledge, they did not touch the screen, press any buttons, or open any apps other than the Phone app.

A few hours later, my iPhone started screen recording by itself. This has happened a few times before and I assumed it was a bug, but given the earlier situation it has made me concerned.

This is an iPhone 11. Is it possible for an iPhone to be compromised in this way? Are there any checks or steps to confirm the device is secure?