What is the ruling on someone who entered a state of ihram from the miqat to perform 'Umrah, but then abandoned his ihram due to losing his residency permit and fearing the police, and was unable to enter Makkah?

You are still in the state of ihram, and you must remove your clothes and head to Makkah to complete the Umrah. Losing your residency permit is not an excuse; you can obtain a replacement or prove your residency by other means. If you are unable to go, and you stipulated at the time of ihram that your place of exit from ihram is where you are detained, then you may exit ihram freely. However, if you did not stipulate this and are unable to complete the Umrah, and you fear harm, then you are considered to be "prevented" (muhasar) and you should exit ihram as one who is prevented.

You have committed the transgression of wearing sewn clothes, and a fidyah (expiation) is incumbent upon you, with the choice of either fasting for three days, or feeding six poor persons, or sacrificing a sheep. However, if you were ignorant of the ruling, then, according to the preponderant opinion of jurists, no fidyah is incumbent upon you.