No, burn in would be seeing the image when the phone was powered
OFF. See
This Page.
LCDs don't burn in, they get temporary persistent images. But these disappear the first time you show a couple mostly white pages, such as loading a web page.
LCDs take power to make BLACK. (or Red or Green or Blue). Displaying pure white turns off the segments completely, allowing the back-light to show through.
They energize LCD segments that they want to be dark, rather than the segments they want to be light like OLED. (This is why people using dark themes on a HOX use more battery that people using brighter themes.)
Sometimes these segments of LDC lose their ability to relax after long sessions of displaying black. But simply painting a few varying images restores this. Its almost never permanent.