You may not necessarily have honey fungus so don’t worry just yet! Abutilon are tropical or sub-tropical plants and can withstand temperatures to about -5C but may well have struggled this winter. Once the plant has died any number of beneficial fungi and bacteria can feed off the dead material. Also, Abutilon species are noted for being more resistant to honey fungus than many other plant species.
If you’re still worried, peel back the bark at the base of the plant - if there is a thin layer of white inside, this may be an indication of honey fungus. Also keep an eye out in late summer and autumn for any toadstools.