What if he got a guilty conscience and brought it back?

如果他问心有愧把它带回来呢？

《柯林斯英汉双解大词典》

For some others it was little more than an attempt to assuage a guilty conscience.

对于其他一些人来说，不过是减缓自己负罪感的一次尝试。

youdao

But the recipients of their largesse are unlikely to care if the donors are motivated by altruism, public relations or a guilty conscience.

但不论捐赠者是因为利他主义的动机，还是因为公共关系的需要，或者是良心的愧疚而捐赠，对于受赠者来说，这一切都无所谓。

youdao

Americans, perhaps because they have a guilty conscience, think of the IRS as being omniscient.

CNN: An Overtaxed IRS

For an eater suffering from a guilty conscience, a spoonful of vitamins makes the fattening food go down.

FORBES: Fructose Nation