Can thieves access my data on a lost iPhone?

Since you have a passcode in place, the thieves basically cannot access your iPhone. They will need to guess your passcode within 10 attempts which is nearly impossible, before it erases all its data.

You will probably receive some messages claiming to be from Apple or Apple Support stating that your iPhone has been located or found. Do not interact with those messages, they are a scam. The thieves are trying to get you to remove Find My off your iPhone, making it fully usable to them.

I would advise you to turn on Lost Mode, report the iPhone stolen to your carrier and local law enforcement. Also if your iPhone does happen to show up in Find My, do not try to retrieve it. This can put your safety at risk, instead tell local law enforcement.

Also please view the following article:

If your iPhone or iPad was stolen - Apple Support

As long as your phone was locked and protected by a secure passcode (known only to you and not easily guessed) …

… the security of the data on your phone is truly the least of your worries.

Your 1st worry — especially If you had a nanoSIM — DO beware of phishing schemes who claim to be “Apple” and claiming to have found your phone.

These messages are from the criminals trying to break-into your phone AND to takeover your Apple Account.

Next, start working thru the steps here;

Find your lost iPhone or iPad - Apple Support

If your iPhone or iPad was stolen - Apple Support

Faheemabbasi04 wrote:

Lost mode is turned on . Should i erase phone or not ? How does erasing works ? Does erasing makes phone unlocked ? If y have any authentic information kindly share

Only do so if you have an iCloud Backup, so in the case you recover your iPhone, you can restore from that. Also erasing all your data will fully ensure the thieves cannot access your data, because it will all be removed from the iPhone. The iPhone will still be unusable to the thieves, just don't remove it from Find My.

In my opinion, if the thieves pickpocketed you or stole it, it was likely to re-sell it to unofficial dealers and not to steal your data. In this case they would erase it themselves in order to sell it or to sell the individual components, but rest assured because before that happens your iPhone would have already synced to iCloud to save everything so even if they erase the individual iPhone, your data on your iCloud could never be deleted without having your Apple ID password and email, and that goes without saying that they pass your 6 digit long iPhone password (which would have 1,000,000 possible combinations).

Zachyy said in his reply that.....

"erasing all your data will fully ensure the thieves cannot access your data, because it will all be removed from the iPhone."

The phone will still remain locked, even though the data on the phone has been erased.

“Erasing” does NOT unlock the phone.

As long as the phone remains on your Apple Account … it will remain unusable by anyone else.

A secure iPhone passcode can keep governments out!

The phone’s built-in defenses are WHY the phishing schemes have become SO advanced … it’s the ONLY way “in.”

And the schemes are specifically designed to prey on one’s natural anxiety about the security of their data.

An individual who remains calm … can “see right thru the phishing scheme.”

👍