Let me shed some light on this tricky German sentence. The reflexive verb is "sich vorkommen", which simply means "feel" in this sentence, and of course, it is not reflexive in English. Many German reflexive verbs are not reflexive in English. There are even verbs in German that cannot be expressed as verbs, but only as adjectives in English. Welll, back to our reflexive verb "sich vorkommen". Unfortunately, it is also a separable verb, meaning the prefix "vor" splits off and goes to the end of the sentence when the verb is conjugated as in "ich komme mir .... vor", "du kommst dir .... vor", "er kommt sich ..... vor", etc. So how did Lars feel in this sentence? "unendlich verlassen", which means "incredibly lonely". Hence, the sentence "Lars kam sich unendlich verlassen vor" means "Lars felt incredibly lonely."
Viel Spass noch beim Lesen!