ZDV Controller described an airspace incursion event resulting from inappropriate point out efforts.

Narrative

Current sector had recently combined with another sector and was busy. A partially rated D-Side sat down; was briefed; and began working. A short time later an aircraft made a request for a lower altitude. The RADAR Controller put a Data Block on the controller display and told the D-Side to point out Aircraft X descending to FL300 which was annotated in the Data Block. The D-Side replied it was done. The R-Side queried and verified the point out was done with the D-Side. The answer was affirmative. The aircraft was observed descending out FL340 when the D-Side asked the R-Side if Aircraft X was pointed out to the sector below. Realizing the miss communication; the R-Side immediately called the sector below who responded he was watching the Aircraft X and he was point out approved. Remind the controllers involved to use the appropriate methods for communications and point outs to include physically pointing to the RADAR controllers MDM as necessary to make sure they are both communicating about the correct aircraft.