the ej22, 2.2L engine will take a lot of abuse. that it why i love it.
it is in fact the perfect engine for an ''outback'' car in the ''great outback down under''. takes a lot of abuse and keeps running, easy to work on, and if it is a 90 - 96, it is a noninterference engine so no damage if the t-belt fails.
depending on the engine year, the ''knock'' you heard may have been HLA noise , not rod bearing noise. low oil levels will cause them to clatter. but letting it idle will usually pump them up again , eliminate the noise and with no damage.
drive it. what have you got to lose? is the sale price going to change if it dies? would you sell it now, as is, without informing the buyer?
if it dies , it dies. if you run it for a few weeks with no noise then you can sell it with a clear conscience.
the ej22 engine will take a lot of abuse. that is why i love it.
what year is your engine?