Evolution works by environmental pressures, both positive and negative.
In your case, a creature starts off independent of humans. At some point, being seen by humans becomes beneficial. This is your positive environmental pressure. Those in the population who have the "seen by humans" genes have a higher survival rate than the others. The benefit increases and becomes overwhelming (only those seen by humans survive or breed). Not being seen by humans is a negative pressure. Now your creatures are dependent on being seen by humans, since the previous population that could exist without humans has become extinct.
However, what benefit they could get from being seen by humans escapes me. The benefit would need to be extreme for this to happen, otherwise the creatures would easily revert to non-observed by humans. The only example I can think of is a cliff-growing plant whose only natural pollinator is unknown and has become extinct. A team of scientists pollinate these plants every year to stop them from becoming extinct as well. Now any of these plants which are not seen by humans in their lifetime will be unable to reproduce and will die without offspring, but not in 24 hours.