iphone 13 went into self lockdown

If Settings → Privacy & Security → Lockdown Mode is Off, it truly cannot turn itself On without someone physically enabling it and confirming with your passcode or Face/Touch ID.

If you feel an unauthorized person/app is remotely using, controlling or monitoring your device, then that is possible only if you have done one or more of the following Don'ts...

1. Don't hand over an iPhone to kids or to a stranger without Enabling Guided Access
2. Don't share Apple IDs
3. Don't Jailbreak
4. Don't share sensitive information pertaining to your device
5. Don't give in to Phishing
6. Don't plug in your device in Airports and Public places through third-party cables and trust the device. Beware of Juice Jacking. (Especially in India)
7. Don't leave your iPhone unlocked and unattended in public places like offices, schools, malls, etc.

If one of the above is true then quickly change the Apple ID Password and Return iPhone settings to their defaults.

Keep the iPhone updated to the latest iOS always and never Jailbreak. That's it.

iOS / iPadOS devices cannot be hacked or infected with Virus / Malware / Spyware *** unless you have intentionally downloaded spurious software or unauthorized apps directly from the internet and installed them on your device or/and have Jailbroken. 

It (Hacking) also depends on how careful you are in sharing sensitive and valuable information pertaining to your iPhone such as Passcode, Password, etc with your friends and family members.

Be judicious when sharing the device's sensitive and valuable information with friends and family members.

**The primary reason for this is Sandboxing. All third-party apps are “sandboxed”, so they are restricted from accessing files stored by other apps or from making changes to the device. Sandboxing is designed to prevent apps from gathering or modifying information stored by other apps.

Security of runtime process in iOS and iPadOS - Apple Support

The sandbox on an iPhone is a security feature that creates a restricted environment for each app to run in isolation from other apps and the operating system. It is a core component of iOS's security architecture and plays a crucial role in making iPhones more secure.

If you doubt the authenticity of the information provided earlier, you have two alternatives:

1. Report the hacking incident to local law enforcement authorities and actively pursue the case.
2. Accept the credibility of the information; it is impervious to hacking. Just as some individuals hold unconventional beliefs, such as a flat Earth or moon landing denial, one has the freedom to believe in anything. The choice ultimately rests with you in this open and free world.

See the pic below which is self-explanatory

Probably you have "Always" Ticked in place of "Away from Familiar Location"

For enhanced security, there's a one-hour delay when changing your location settings from "Always" to "Away from Familiar Location." This applies even if you use Face ID for authentication.



A delay will be required when you are not at a familiar location, such as your home or work, to change security settings.

Know more --> About Stolen Device Protection for iPhone

Simply adding a location to your contact card (e.g., marking it as "Home") does not automatically make it a "Familiar Location" in the context of iPhone's location-based learning and features.

Why Adding "Home" to the Contact Card Isn't Enough:

1. Trust and Validation: Adding an address to your contact card can be done manually or by anyone with access to your phone, but the iPhone uses activity-based learning to validate locations it deems "familiar."
2. Behavior-Based Learning: iPhones utilize machine learning and location tracking (if enabled) to recognize patterns of frequent visits. It identifies "Familiar Locations" based on where the phone spends significant time during specific periods, like overnight stays or long durations.

What You Can Do:

1. Spend Time at the Location: Use your iPhone at your new address consistently, especially during the hours you'd normally be home (e.g., evening and night). Over time, the iPhone will learn this as a familiar location.
2. Enable Location Services:
   1. Go to Settings > Privacy & Security > Location Services and ensure it's turned on.
   2. Make sure "Significant Locations" (under System Services) is enabled. This helps the iPhone learn frequently visited locations.
3. Ensure GPS Accuracy: Poor GPS accuracy can delay location recognition. Make sure your iPhone is connected to Wi-Fi, as this improves location precision indoors.

By doing this, the iPhone will naturally associate the address with your routines, and over time, it will classify it as a "Familiar Location."

You will need to clarify what you mean by "lockdown for 10 hours", as Lockdown mode does not make your device unusable.

Neither MalwareBytes and any other app is capable of scanning your device to detect any problems.

Please clarify.

Assuming you mean it is "unavailable" or "disabled", you haven't been hacked. Someone entered the passcode incorrectly too many times.

Even if that is not what you mean, you have not been "hacked".