I just read a manga where by context a girl broke up with her boyfriend. She says this.
逃げられたの 彼氏に!!
仕事に入れ込みすぎだって
Why is 彼氏に used alongside the verb?
逃げられたの 彼氏に!!
As you've noticed, this is an inverted word order of:
彼氏に逃げられたの
逃げられた here is Suffering Passive (迷惑の受身), which is a kind of Indirect Passive (間接受身).
As you know, in passive sentences the agent (動作主) of the action is marked with に. eg お母さんが私を褒める → 私がお母さんに褒められる. Here the agent of 逃げる is 彼氏, hence:
彼氏が逃げた (active) My boyfriend ran away.
→ 彼氏に逃げられた (indirect passive) My boyfriend ran away from me (which affected me in some way). / My boyfriend up and left (on me).
For more on Suffering Passive / Indirect Passive: